Q.What is a stored procedure ?
A stored procedure is a sequence of statements that perform specific function.
A stored procedure is a named pl/sql block which performs an action.It is stored in the database as a schema object and can be repeatedly executed.It can be invoked, parameterised and nested.
Q.What is SQL*Loader?
SQL*Loader is a product for moving data in external files into tables in an Oracle database. To load data from external files into an Oracle database, two types of input must be provided to SQL*Loader : the data itself and the control file. The control file describes the data to be loaded. It describes the Names and format of the data files, Specifications for loading data and the Data to be loaded (optional). Invoking the loader sqlload username/password controlfilename <options>.
Q.What are the two parts of a procedure ?
the above person have answerd wrong. Or rather the question may be wrong. It should be packages instead of procedures. What are the 2 parts of package ? But the question is what are the 2 parts for procedue!!!
Procedure Specification and Procedure Body.
Q.What is Date Functions?
Date Functions are ADD_MONTHS, LAST_DAY, NEXT_DAY, MONTHS_BETWEEN & SYSDATE.
Q.What is NVL?
NVL: Null value function converts a null value to a non-null value for the purpose of evaluating an expression. Numeric Functions accept numeric I/P & return numeric values. They are MOD, SQRT, ROUND, TRUNC & POWER.
Q.What is Intersect?
Intersect is the product of two tables listing only the matching rows.
Q.How to know the last executed procedure?
Execute procedure name (parameter1,parameter2)
Select timestamps, owner, obj_name, action_name from dba_audit_trail;this statement gives last executed time for procedure , function & package.
Q.What are the Restrictions on Cursor Variables?
Currently, cursor variables are subject to the following restrictions:You cannot declare cursor variables in a package spec. For example, the following declaration is not allowed:CREATE PACKAGE emp_stuff AS TYPE EmpCurTyp IS REF CURSOR RETURN emp%ROWTYPE; emp_cv EmpCurTyp; -- not allowedEND emp_stuff;You cannot pass cursor variables to a procedure that is called through a database link.If you pass a host cursor variable to PL/SQL, you cannot fetch from it on the server side unless you also open it there on the same server call.You cannot use comparison operators to test cursor variables for equality, inequality, or nullity.You cannot assign nulls to a cursor variable.Database columns cannot store the values of cursor variables. There is no equivalent type to use in a CREATE TABLE statement.You cannot store cursor variables in an associative array, nested table, or varray.Cursors and cursor variables are not interoperable; that is, you cannot use one where the other is expected. For example, you cannot
reference a cursor variable in a cursor FOR loop
Q.What is Minus?
Minus is the product of two tables listing only the non-matching rows.
Q.What are the cursor attributes used in PL/SQL?
% ISOPEN - To check whether cursor is open or not
% ROWCOUNT - Number of rows fetched/updated/deleted.
% FOUND - To check whether cursor has fetched any row. True if rows are fetched.
% NOT FOUND - To check whether cursor has fetched any row. True if no rows are featched.
These attributes are proceeded with SQL for Implicit Cursors and with Cursor name for Explicit Cursors.
Q.What is Consistency?
consistency: states that until commit the data will not be reflected to other users,in order to maintain proper consistency.
consider a example: if user A transfer money to user B. The changes are updates in A account (debit) but until it will be updated in B (credit) too till then others will not be able to see the debit of A. when debit to A and credit to B happen then one can see the updates hence maintain consistency
Q.What are % TYPE and % ROWTYPE? What are the advantages of using these over data types?
% TYPE provides the data type of a variable or a database column to that variable.
% ROWTYPE provides the record type that represents a entire row of a table or view or columns selected in the cursor.
The advantages are : I. Need not know about variable's data type
ii. If the database definition of a column in a table changes, the data type of a variable changes accordingly.
Q.What will the Output for this Coding
Declare
Cursor c1 is select * from emp FORUPDATE;
Z c1%rowtype;
Begin
Open C1;
Fetch c1 into Z;
Commit;
Fetch c1 in to Z;
end;
By declaring this cursor we can update the table emp through z,means wo not need to write table name for updation,it may be only by "z".
By issuing the TCL like commit or rollback, the cursor will be closed automatically, you cannat fetch again. You will get an error if you
Q.What is Commit?
Commit is an event that attempts to make data in the database identical to the data in the form. It involves writing or posting data to the database and committing data to the database. Forms check the validity of the data in fields and records during a commit. Validity check are uniqueness, consistency and db restrictions.
Q.Give the structure of the function?
FUNCTION name (argument list .....) Return datatype is
local variable declarations
Begin
executable statements
Exception
execution handlers
End;
Q.What is a cursor ? Why Cursor is required?
Cursor is a named private SQL area from where information can be accessed. Cursors are required to process rows individually for queries returning multiple rows.
Q.If the application is running very slow? At what points you need to go about the database in order to improve the performance?
For improving performance, we need to check the sql statement blocks , because for every sql satement execution transfor to sql engine and come back to plsq engine that process takes more time to process the plsql block.
Q.What are advantages fo Stored Procedures?
Extensibility,Modularity, Reusability, Maintainability and one time compilation.
Q.What is difference b/w stored procedures and application procedures, stored function and application function?
Stored procedures are subprogrammes stored in the database and can be called &executee multiple times wherein an application procedure is the one being used for a particular application same is the way for function.
Both can be executed any number of times. Only difference is that stored procedures/ functions are stored in database in complied format while the application procedures/functions are not in precomplied format and at run time has to be compiled.
Q.What is a cursor ? Why Cursor is required?
Cursor is a named private SQL area from where information can be accessed. Cursors are required to process rows individually for queries returning multiple rows.
Q.State the difference between implicit and explicit cursor's.
Implicit Cursor are declared and used by the oracle internally. whereas the explicit cursors are declared and used by the user. more over implicitly cursors are no need to declare oracle creates and process and closes autometically. the explicit cursor should be declared and closed by the user.
Q.How to avoid using cursors? What to use instead of cursor and in what cases to do so?
just use subquery in for clause
ex:
for emprec in (select * from emp)
loop
dbms_output.put_line(emprec.empno);
end loop;
no exit statement needed
implicit open,fetch,close occurs
Q.What is pl/sql?what are the advantages of pl/sql?
PL/SQL(a product of Oracle) is the 'programming language' extension of sql.
It is a full-fledged language although it is specially designed for database centric activities.
Q.How to disable multiple triggers of a table at at a time?
ALTER TABLE<TABLE NAME> DISABLE ALL TRIGGER
Q.How many types of database triggers can be specified on a table ? What are they ?
Insert Update Delete
Before Row o.k. o.k. o.k.
After Row o.k. o.k. o.k.
Before Statement o.k. o.k. o.k.
After Statement o.k. o.k. o.k.
If FOR EACH ROW clause is specified, then the trigger for each Row affected by the statement.
If WHEN clause is specified, the trigger fires according to the returned Boolean value.
Q.Explain how procedures and functions are called in a PL/SQL block ?
Function can be called from SQL query + explicitly as well
e.g 1)select empno,salary,fn_comm(salary)from employee;
2)commision=fn_comm(salary);
Procedure can be called from begin-end clause.
e.g.
Begin
(
proc_comm(salary);
)
end
Function is called as part of an expression.
sal := calculate_sal ('a822');
procedure is called as a PL/SQL statement
calculate_bonus ('A822');
Q.What will happen after commit statement ?
Cursor C1 is
Select empno,
ename from emp;
Begin
open C1; loop
Fetch C1 into
eno.ename;
Exit When
C1 %notfound;-----
commit;
end loop;
end;
The cursor having query as SELECT .... FOR UPDATE gets closed after COMMIT/ROLLBACK.
The cursor having query as SELECT.... does not get closed even after COMMIT/ROLLBACK.
Q.What happens if a procedure that updates a column of table X is called in a database trigger of the same table ?
Trigger will be called... Based on the event what trigger as to do. if trigger is also doing the same update statment then Mutating Table occurs. if trigger is not doing any DML statment nothing happens just Trigger will be called..
Q.Can we declare a column having number data type and its scale is larger than pricesion
ex: column_name NUMBER(10,100),
column_name NUMBAER(10,-84)
Yes,
we can declare a column with above condition.
table created successfully.
Q.The IN operator may be used if you know the exact value you want to return for at least one of the columns.
SELECT column_name FROM table_name WHERE column_name IN (value1,value2,..)
Q.What is SQL Deadlock?
Deadlock is a unique situation in a multi user system that causes two or more users to wait indefinitely for a locked resource. First user needs a resource locked by the second user and the second user needs a resource locked by the first user. To avoid dead locks, avoid using exclusive table lock and if using, use it in the same sequence and use Commit frequently to release locks.
Q.Where the Pre_defined_exceptions are stored ?
In the standard package.
Procedures, Functions & Packages ;
Q. Below is the table
city gender name
delhi male a
delhi female b
mumbai male c
mumbai female d
delhi male e
I want the o/p as follows:
male female
delhi 2 1
mumbai 1 1
Please help me in writing the query that can yield the o/p mentioned above?
select city, sum(decode(gender,'male',1,0)) Male_cnt, sum(gender,'female',1,0) female_cnt
from table_name
group by city
select a.city,a.male,b.female from
(select city,count(gender) male from city where gender='m'group by city,gender)a
join
(select city,count(gender) female from city where gender='f' group by city,gender)b
on a.city=b.city
Q.What is Sequences?
Sequences are used for generating sequence numbers without any overhead of locking. Drawback is that after generating a sequence number if the transaction is rolled back, then that sequence number is lost
Q.What are % TYPE and % ROWTYPE ? What are the advantages of using these over datatypes?
% TYPE provides the data type of a variable or a database column to that variable.
% ROWTYPE provides the record type that represents a entire row of a table or view or columns selected in the cursor.
The advantages are : I. Need not know about variable's data type
ii. If the database definition of a column in a table changes, the data type of a variable changes accordingly.
Q.What is Mutating SQL Table?
Mutating Table is a table that is currently being modified by an Insert, Update or Delete statement. Constraining Table is a table that a triggering statement might need to read either directly for a SQL statement or indirectly for a declarative Referential Integrity constraints. Pseudo Columns behaves like a column in a table but are not actually stored in the table. E.g. Currval, Nextval, Rowid, Rownum, Level etc.
Q.What is PL/SQL table ?
Objects of type TABLE are called "PL/SQL tables", which are modeled as (but not the same as) database tables, PL/SQL tables use a primary PL/SQL tables can have one column and a primary key.
Cursors
PL/SQL tables are PL/SQL?s way of providing arrays. Arrays are like tem-porary
tables in memory and thus are processed very quickly. It is impor-tant
for you to realize that they are not database tables, and DML
statements cannot be issued against them. This type of table is indexed
by a binary integer counter (it cannot be indexed by another type of
number) whose value can be referenced using the number of the index.
Remember that PL/SQL tables exist in memory only, and therefore don't
exist in any persistent way, disappearing after the session ends.
A PL/SQL TABLE DECLARATION
There are two steps in the declaration of a PL/SQL table. First, you must define the table structure using the TYPE statement. Second, once a table type is created, you then declare the actual table.
FOR EXAMPLE
DECLARE
-- Table structure definition
TYPE NameType IS TABLE OF
Customer.name_name%TYPE
INDEX BY BINARY_INTEGER;
-- Create the actual table
CnameTab NameType;
KnameTab NameType;
BEGIN
NULL; -- ...
END;
Q.In a Distributed Database System Can we execute two queries simultaneously? Justify?
Yes, Distributed database system based on 2 phase commit,one query is independent of 2 nd query so of course we can run.
Q.What are the modes of parameters that can be passed to a procedure ?
IN parameter is the default mode which acts as a constant inside calling environment.value passed in this parameter can not be changed.OUT parameter mode is used to pass value from calling environment into main block,here we can change the value.It acts as a variable inside calling environment.
INOUT parameter mode which pass value into calling environment and will get the value back in main block.
IN parameter mode uses call by reference method to pass value from formal parameter to actual parameter.
OUT & INOUT parameter mode uses call by value method to pass values.
IN,OUT,IN-OUT parameters.
Q.Name the tables where characteristics of Package, procedure and functions are stored?
User_objects, User_Source and User_error.
Q.How many types of database triggers can be specified on a table? What are they?
Insert Update Delete
Before Row o.k. o.k. o.k.
After Row o.k. o.k. o.k.
Before Statement o.k. o.k. o.k.
After Statement o.k. o.k. o.k.
If FOR EACH ROW clause is specified, then the trigger for each Row affected by the statement.
If WHEN clause is specified, the trigger fires according to the returned Boolean value.
Q.How can a function retun more than one value in oracle with proper example?
Basically as per property of function it has to return one value. So the other values can be returned from the out parameter of the function.
But its advised if you want more that one return value go for procedure however function will also yield the same result.
Q.Explain If the entire disk is corrupted how will you and what are the steps to recover the database?
if the entire disk is corrupted and no backup is there don nothing sit and relax their is no possibility of recovery ...a backup is required for restoration and for recovery redo log and archive logs.
Once if you have theses than think of recovering ..a dba should always plan for the recovery scenario depending upon the criticality of the database.oracle provides 0% data loss facilty through data guard and online backup .its dba who has to decide.
Q.What is Rollback?
Rollback causes work in the current transaction to be undone.
Q.What is a cursor for loop ?
Cursor for loop implicitly declares %ROWTYPE as loop index,opens a cursor, fetches rows of values from active set into fields in the record and closes when all the records have been processed.
eg. FOR emp_rec IN C1 LOOP
salary_total := salary_total +emp_rec sal;
END LOOP;
Q.How to sort the rows in SQL?
Sort the Rows:
SELECT column1, column2, ... FROM table_name ORDER BY columnX, columnY, ..
SELECT column1, column2, ... FROM table_name ORDER BY columnX DESC
SELECT column1, column2, ... FROM table_name ORDER BY columnX DESC, columnY ASC1.
select column1,column2,column3 from table1
where
column1>10
order by 1,3,2;
Inthis case it sorts based on the columns' position in the select query i.e. in the above query it will sort first based on column1 then on column3 and then by column2. By default the sort is in ascending order, if you want it to be in descending order, you need to specify the key word DESC in ORDER BY clause.
2.select * from emp order by eno desc;
You can sort your results based on any column in the tables because you are select all the columns.
3.select eno,ename from emp order by deptno;
This is wrong because the column deptno is not present in the select clause.
Q.What is Pragma EXECPTION_INIT? Explain the usage?
The PRAGMA EXECPTION_INIT tells the complier to associate an exception with an oracle error. To get an error message of a specific oracle error.
e.g. PRAGMA EXCEPTION_INIT (exception name, oracle error number
Q.What's the use of dyanamic sql in oracle?
Dynamic SQL enables you to write programs that reference SQL statements whose full text is not known until runtime.
Q.How we can create a table in PL/SQL block. insert records into it? is it possible by some procedure or function? please give example?
CREATE OR REPLACE PROCEDURE ddl_create_proc (p_table_name IN VARCHAR2)
AS
l_stmt VARCHAR2(200);
BEGIN
DBMS_OUTPUT.put_line('STARTING ');
l_stmt := 'create table '|| p_table_name || ' as (select * from emp )';
execute IMMEDIATE l_stmt;
DBMS_OUTPUT.put_line('end ');
EXCEPTION
WHEN OTHERS THEN
DBMS_OUTPUT.put_line('exception '||SQLERRM || 'message'||sqlcode);
END;
Q.What is a JOIN?
JOIN is the form of SELECT command that combines info from two or more tables.
Types of Joins are Simple (Equijoin & Non-Equijoin), Outer & Self join.
Equijoin returns rows from two or more tables joined together based upon a equality condition in the WHERE clause.
Non-Equijoin returns rows from two or more tables based upon a relationship other than the equality condition in the WHERE clause.
Outer Join combines two or more tables returning those rows from one table that have no direct match in the other table.
Self Join joins a table to itself as though it were two separate tables.
Q.what is the starting oracle error number?
what is meant by forward declaration in functions?
One must declare an identifier before referencing it. Once it is declared it can be referred even before defining it in the PL/SQL. This rule applies to function and procedures also.
Q.Can we declare a column having number data type and its scale is larger than pricesion
ex: column_name NUMBER(10,100),
column_name NUMBAER(10,-84)
No, you cant. May be your table might be created successfully but if you try to insert values it will shows you an error.
Numeric or Value Error
NUMBER (p,s)
p- precision, which is the total size of digits
s- scale , which represents the total number of digits that are present to the right side of the decimal.
s should be strictly less than p. If I am missing somthing. Please fill me in.
Yes,we can declare a column with above condition.table created successfully.
yes, 100 is the total size and 10 is included in 100
Q.Is it possible to use Transaction control Statements such a ROLLBACK or COMMIT in Database Trigger? Why?
It is not possible. As triggers are defined for each table, if you use COMMIT of ROLLBACK in a trigger, it affects logical transaction processing.
yes WE can use COMMIT and ROLLBACK triggers, but by using PRAGAMA AUTONAMOUS_TRANSATIONS. Now the transation treated as a autonomous tansation.
Q.What is COLUMN?
COLUMN command define column headings & format data values.
Q.SELECT statements in SQL?
SELECT column_name(s) FROM table_name
SELECT DISTINCT column_name(s) FROM table_name
SELECT column FROM table WHERE column operator value
SELECT column FROM table WHERE column LIKE pattern
SELECT column,SUM(column) FROM table GROUP BY column
SELECT column,SUM(column) FROM table GROUP BY column HAVING SUM(column) condition value
Note that single quotes around text values and numeric values should not be enclosed in quotes. Double quotes may be acceptable in some databases.
Q.What is the Delete Statements in SQL?
Delete statement in SQL is used to delete partial/all data.
Especially delete statement is useful in case of partial delete depending upon our criterias otherwise use TRUNCATE to delete whole data from table.
When delete command fires then:
1) Triggers will fire (If created on that table)
2) This will not auto commit changes made So there is one chance to rollback.
3) If u delete whole data then HWM (Highest Water Mark) will not change which gets changed in case of Truncate.
Q.What is Posting?
Posting is an event that writes Inserts, Updates & Deletes in the forms to the database but not committing these transactions to the database.
Q.Where the Pre_defined_exceptions are stored?
In the standard package.
Procedures, Functions & Packages ;
Q.What are two parts of package?
The two parts of package are PACKAGE SPECIFICATION & PACKAGE BODY. Package Specification contains declarations that are global to the packages and local to the schema.
Package Body contains actual procedures and local declaration of the procedures and cursor declarations.
Q.What are the datatypes a available in PL/SQL?
Some scalar data types such as
NUMBER,
VARCHAR2,
DATE,
CHAR,
LONG,
BOOLEAN.
Some composite data types such as RECORD & TABLE.
Q.What is an Exception? What are types of Exception?
Exception is the error handling part of PL/SQL block. The types are Predefined and user defined. Some of Predefined exceptions are.
CURSOR_ALREADY_OPEN
DUP_VAL_ON_INDEX
NO_DATA_FOUND
TOO_MANY_ROWS
INVALID_CURSOR
INVALID_NUMBER
LOGON_DENIED
NOT_LOGGED_ON
PROGRAM-ERROR
STORAGE_ERROR
TIMEOUT_ON_RESOURCE
VALUE_ERROR
ZERO_DIVIDE
OTHERS.
exception is an identifier and error handling part of pl/sql types := 1)predifined 2) user defined.
Q.Explian rowid, rownum?what are the psoducolumns we have?
ROWID - Hexa decimal number each and every row having unique.Used in searching.
ROWNUM - It is a integer number also unique for sorting Normally TOP N Analysys.
Other Psudo Column are
NEXTVAL,CURRVAL Of sequence are some exampls
psudo columns are default columns provided by oracle
Q.How to avoid using cursors? What to use instead of cursor and in what cases to do so?
Just use subquery in for clause
ex:For emprec in (select * from emp)
loop
dbms_output.put_line(emprec.empno);
end loop;
no exit statement needed
implicit open,fetch,close occurs
Q.what is the starting oracle error number?
what is meant by forward declaration in functions?
One must declare an identifier before referencing it. Once it is declared it can be referred even before defining it in the PL/SQL. This rule applies to function and procedures also
ORA-20000
Q.What are the components of a PL/SQL block?
A set of related declarations and procedural statements is called block.
DECLARE -- declaration section BEGIN -- executable statements -- main section EXCEPTION -- handling possible exceptions -- occuring in the main section END;
Q.What is difference between stored procedures and application procedures,stored function and application function?
Stored procedures are sub programs stored in the database and can be called & execute multiple times where in an application procedure is the one being used for a particular application same is the way for function
Procedure:-
Execute as a PL/SQL
statement,No RETURN clause in
the header,Can return none, one,
or many values,Can contain a RETURN
statement
Function:-Invoke as part of an
expression,Must contain a RETURN
clause in the header,Must return a single value,Must contain at least one RETURN statement
Q.What is Raise_application_error ?
Raise_application_error is a procedure of package DBMS_STANDARD which allows to issue an user_defined error messages from stored sub-program or database
trigger.
Q.What is trigger,cursor,functions in pl-sql and we need sample programs about it?
Trigger is an event driven PL/SQL block. Event may be any DML transaction.
Cursor is a stored select statement for that current session. It will not be stored in the database, it is a logical component.
Function is a set of PL/SQL statements or a PL/SQL block, which performs an operation and must return a value.
Q.How we can create a table in PL/SQL block. insert records into it??? is it possible by some procedure or function?? please give example...
CREATE OR REPLACE PROCEDURE ddl_create_proc (p_table_name IN VARCHAR2)
AS
l_stmt VARCHAR2(200);
BEGIN
DBMS_OUTPUT.put_line('STARTING ');
l_stmt := 'create table '|| p_table_name || ' as (select * from emp )';
execute IMMEDIATE l_stmt;
DBMS_OUTPUT.put_line('end ');
EXCEPTION
WHEN OTHERS THEN
DBMS_OUTPUT.put_line('exception '||SQLERRM || 'message'||sqlcode);
END;
Q.In pl/sql functions what is use of out parameter even though we have return statement.
With out parameters you can get the more than one out values in the calling program. It is recommended not to use out parameters in functions. If you need more than one out values then use procedures instead of functions.
Q.How to debug the procedure ?
You can use DBMS_OUTPUT oracle supplied package or DBMS_DEBUG pasckage.
Q.What is ref cursor?
In PL/SQL ,pointer has a datatype REF X where
REF-Reference
X-class of objects
Cursor Variables has a datatype REF-CURSOR
where Cursor Varibales are like pointers which hold the memory location of some item instead of the item itself.
Q.State the advantage and disadvantage of Cursor?
Advantage :
In pl/sql if you want perform some actions more than one records you should user these cursors only. bye using these cursors you process the query records. you can easily move the records and you can exit from procedure when you required by using cursor attributes.
disadvantage:
using implicit/explicit cursors are depended by sutiation. if the result set is les than 50 or 100 records it is better to go for implicit cursors. if the result set is large then you should use exlicit cursors. other wise it will put burdon on cpu.
Q.What is a database trigger ? Name some usages of database trigger ?
A database triggers is stored PL/SQL program unit associated with a specific database table or view. The code in the trigger defines the action the database needs to perform whenever some database manipulation (INSERT, UPDATE, DELETE) takes place.
Unlike the stored procedure and functions, which have to be called explicitly, the database triggers are fires (executed) or called implicitly whenever the table is affected by any of the above said DML operations.
Till oracle 7.0 only 12 triggers could be associated with a given table, but in higher versions of Oracle there is no such limitation. A database trigger fires with the privileges of owner not that of user
A database trigger has three parts
1. A triggering event
2. A trigger constraint (Optional)
3. Trigger action
A triggering event can be an insert, update, or delete statement or a instance shutdown or startup etc. The trigger fires automatically when any of these events occur A trigger constraint specifies a Boolean expression that must be true for the trigger to fire. This condition is specified using the WHEN clause. The trigger action is a procedure that contains the code to be executed when the trigger fires.
Database trigger is stored PL/SQL program unit associated with a specific database table. Usages are Audit data modifications, Log events transparently, Enforce complex business rules Derive column values automatically, Implement complex security authorizations. Maintain replicate tables.
Q.What are the return values of functions SQLCODE and SQLERRM ?
SQLCODE returns the latest code of the error that has occurred.
SQLERRM returns the relevant error message of the SQLCODE.
Q.How packaged procedures and functions are called from the following?
a. Stored procedure or anonymous block
b. an application program such a PRC *C, PRO* COBOL
c. SQL *PLUS
a.PACKAGE NAME.PROCEDURE NAME (parameters);
variable := PACKAGE NAME.FUNCTION NAME (arguments);
EXEC SQL EXECUTE
b.
BEGIN
PACKAGE NAME.PROCEDURE NAME (parameters)
variable := PACKAGE NAME.FUNCTION NAME (arguments);
END;
END EXEC;
c. EXECUTE PACKAGE NAME.PROCEDURE if the procedures does not have any out/in-out parameters. A function can not be called.
Q.Operators used in SELECT statements are?
= Equal
<> or != Not equal
> Greater than
< Less than
>= Greater than or equal
<= Less than or equal
BETWEEN Between an inclusive range
LIKE Search for a pattern
Q.Give the structure of the procedure ?
basically procedure has three
parts
1.variable declaretion(optional)
2.body(mandetory)
3.Exception(optional)
suppose ex
CREATE OR REPLACEPROCEDURE emp_pro( p_id IN employees.employee_id%TYPE)
IS
v_name employees.last_name%TYPE;
v_mail employees.email%TYPE;
BEGIN
SELECT last_name,email INTO v_name,v_mail FROM employees
WHERE employee_id:=p_id;
DBMS_OUTPUT.PUT_LINE('NAME:'||v_name ||'MAILID:'||v_mail);
END;
/
PROCEDURE name (parameter list.....)
is
local variable declarations
BEGIN
Executable statements.
Exception.
exception handlers
end;
Q.What is SPOOL?
spool command used for printing the out put of the sql statments in a file. Eg.
spool /tmp/sql_out.txt
select emp_name, emp_id from emp where dept='sales';
spool off;
we can see the out on /tmp/sql_out.txt file.
SPOOL command creates a print file of the report.
Q.What are advantages fo Stored Procedures
Extensibility,Modularity, Reusability, Maintainability and one time compilation.
Q.IS Stored Function Is Pre-Compiled as Stored Procedure ? If No Why
stored procedure means the pre-compiled precedure ,which is used for a specific action to be executed more than one times whenever you called from coding in the programe.
stored procedure is an important concept in the application developement in oracle.
Q.Explain the two type of Cursors ?
There are two types of cursors, Implicit Cursor and Explicit Cursor.
PL/SQL uses Implicit Cursors for queries. User defined cursors are called Explicit Cursors. They can be declared and used.
Q.What is Overloading of procedures ?
Overloading of procedure
name of the procedure is
same but the number of parameters should be different.In that case,procedure will be overloaded.
2. if the number of parameters are same in that case,data type should be different.
if the two rules are satisfied in that case procedure will be overloaded.
Q.What is PL/SQL ?
PL/SQL is a procedural language that has both interactive SQL and procedural programming language constructs such as iteration, conditional branching.
Q.What are the PL/SQL Statements used in cursor processing ?
DECLARE CURSOR cursor name, OPEN cursor name, FETCH cursor name INTO or Record types, CLOSE cursor name.
Q.What is Set Transaction?
Set Transaction is to establish properties for the current transaction.
Q.What is Character Functions?
Character Functions are INITCAP, UPPER, LOWER, SUBSTR & LENGTH. Additional functions are GREATEST & LEAST. Group Functions returns results based upon groups of rows rather than one result per row, use group functions. They are AVG, COUNT, MAX, MIN & SUM.
Q.What is an Exception ? What are types of Exception?
Exception is the error handling part of PL/SQL block. The types are Predefined and user defined. Some of Predefined exceptions are.
CURSOR_ALREADY_OPEN
DUP_VAL_ON_INDEX
NO_DATA_FOUND
TOO_MANY_ROWS
INVALID_CURSOR
INVALID_NUMBER
LOGON_DENIED
NOT_LOGGED_ON
PROGRAM-ERROR
STORAGE_ERROR
TIMEOUT_ON_RESOURCE
VALUE_ERROR
ZERO_DIVIDE
OTHERS.
Q.Is it possible to use Transaction control Statements such a ROLLBACK or COMMIT in Database Trigger? Why?
It is not possible. As triggers are defined for each table, if you use COMMIT of ROLLBACK in a trigger, it affects logical transaction processing.
yes WE can use COMMIT and ROLLBACK triggers, but by using PRAGAMA AUTONAMOUS_TRANSATIONS. Now the transation treated as a autonomous tansation.
Q.What is Multiple columns?
Multiple columns can be returned from a Nested Subquery.
Q.What is Savepoint?
Savepoint is a point within a particular transaction to which you may rollback without rolling back the entire transaction.
A stored procedure is a sequence of statements that perform specific function.
A stored procedure is a named pl/sql block which performs an action.It is stored in the database as a schema object and can be repeatedly executed.It can be invoked, parameterised and nested.
Q.What is SQL*Loader?
SQL*Loader is a product for moving data in external files into tables in an Oracle database. To load data from external files into an Oracle database, two types of input must be provided to SQL*Loader : the data itself and the control file. The control file describes the data to be loaded. It describes the Names and format of the data files, Specifications for loading data and the Data to be loaded (optional). Invoking the loader sqlload username/password controlfilename <options>.
Q.What are the two parts of a procedure ?
the above person have answerd wrong. Or rather the question may be wrong. It should be packages instead of procedures. What are the 2 parts of package ? But the question is what are the 2 parts for procedue!!!
Procedure Specification and Procedure Body.
Q.What is Date Functions?
Date Functions are ADD_MONTHS, LAST_DAY, NEXT_DAY, MONTHS_BETWEEN & SYSDATE.
Q.What is NVL?
NVL: Null value function converts a null value to a non-null value for the purpose of evaluating an expression. Numeric Functions accept numeric I/P & return numeric values. They are MOD, SQRT, ROUND, TRUNC & POWER.
Q.What is Intersect?
Intersect is the product of two tables listing only the matching rows.
Q.How to know the last executed procedure?
Execute procedure name (parameter1,parameter2)
Select timestamps, owner, obj_name, action_name from dba_audit_trail;this statement gives last executed time for procedure , function & package.
Q.What are the Restrictions on Cursor Variables?
Currently, cursor variables are subject to the following restrictions:You cannot declare cursor variables in a package spec. For example, the following declaration is not allowed:CREATE PACKAGE emp_stuff AS TYPE EmpCurTyp IS REF CURSOR RETURN emp%ROWTYPE; emp_cv EmpCurTyp; -- not allowedEND emp_stuff;You cannot pass cursor variables to a procedure that is called through a database link.If you pass a host cursor variable to PL/SQL, you cannot fetch from it on the server side unless you also open it there on the same server call.You cannot use comparison operators to test cursor variables for equality, inequality, or nullity.You cannot assign nulls to a cursor variable.Database columns cannot store the values of cursor variables. There is no equivalent type to use in a CREATE TABLE statement.You cannot store cursor variables in an associative array, nested table, or varray.Cursors and cursor variables are not interoperable; that is, you cannot use one where the other is expected. For example, you cannot
reference a cursor variable in a cursor FOR loop
Q.What is Minus?
Minus is the product of two tables listing only the non-matching rows.
Q.What are the cursor attributes used in PL/SQL?
% ISOPEN - To check whether cursor is open or not
% ROWCOUNT - Number of rows fetched/updated/deleted.
% FOUND - To check whether cursor has fetched any row. True if rows are fetched.
% NOT FOUND - To check whether cursor has fetched any row. True if no rows are featched.
These attributes are proceeded with SQL for Implicit Cursors and with Cursor name for Explicit Cursors.
Q.What is Consistency?
consistency: states that until commit the data will not be reflected to other users,in order to maintain proper consistency.
consider a example: if user A transfer money to user B. The changes are updates in A account (debit) but until it will be updated in B (credit) too till then others will not be able to see the debit of A. when debit to A and credit to B happen then one can see the updates hence maintain consistency
Q.What are % TYPE and % ROWTYPE? What are the advantages of using these over data types?
% TYPE provides the data type of a variable or a database column to that variable.
% ROWTYPE provides the record type that represents a entire row of a table or view or columns selected in the cursor.
The advantages are : I. Need not know about variable's data type
ii. If the database definition of a column in a table changes, the data type of a variable changes accordingly.
Q.What will the Output for this Coding
Declare
Cursor c1 is select * from emp FORUPDATE;
Z c1%rowtype;
Begin
Open C1;
Fetch c1 into Z;
Commit;
Fetch c1 in to Z;
end;
By declaring this cursor we can update the table emp through z,means wo not need to write table name for updation,it may be only by "z".
By issuing the TCL like commit or rollback, the cursor will be closed automatically, you cannat fetch again. You will get an error if you
Q.What is Commit?
Commit is an event that attempts to make data in the database identical to the data in the form. It involves writing or posting data to the database and committing data to the database. Forms check the validity of the data in fields and records during a commit. Validity check are uniqueness, consistency and db restrictions.
Q.Give the structure of the function?
FUNCTION name (argument list .....) Return datatype is
local variable declarations
Begin
executable statements
Exception
execution handlers
End;
Q.What is a cursor ? Why Cursor is required?
Cursor is a named private SQL area from where information can be accessed. Cursors are required to process rows individually for queries returning multiple rows.
Q.If the application is running very slow? At what points you need to go about the database in order to improve the performance?
For improving performance, we need to check the sql statement blocks , because for every sql satement execution transfor to sql engine and come back to plsq engine that process takes more time to process the plsql block.
Q.What are advantages fo Stored Procedures?
Extensibility,Modularity, Reusability, Maintainability and one time compilation.
Q.What is difference b/w stored procedures and application procedures, stored function and application function?
Stored procedures are subprogrammes stored in the database and can be called &executee multiple times wherein an application procedure is the one being used for a particular application same is the way for function.
Both can be executed any number of times. Only difference is that stored procedures/ functions are stored in database in complied format while the application procedures/functions are not in precomplied format and at run time has to be compiled.
Q.What is a cursor ? Why Cursor is required?
Cursor is a named private SQL area from where information can be accessed. Cursors are required to process rows individually for queries returning multiple rows.
Q.State the difference between implicit and explicit cursor's.
Implicit Cursor are declared and used by the oracle internally. whereas the explicit cursors are declared and used by the user. more over implicitly cursors are no need to declare oracle creates and process and closes autometically. the explicit cursor should be declared and closed by the user.
Q.How to avoid using cursors? What to use instead of cursor and in what cases to do so?
just use subquery in for clause
ex:
for emprec in (select * from emp)
loop
dbms_output.put_line(emprec.empno);
end loop;
no exit statement needed
implicit open,fetch,close occurs
Q.What is pl/sql?what are the advantages of pl/sql?
PL/SQL(a product of Oracle) is the 'programming language' extension of sql.
It is a full-fledged language although it is specially designed for database centric activities.
Q.How to disable multiple triggers of a table at at a time?
ALTER TABLE<TABLE NAME> DISABLE ALL TRIGGER
Q.How many types of database triggers can be specified on a table ? What are they ?
Insert Update Delete
Before Row o.k. o.k. o.k.
After Row o.k. o.k. o.k.
Before Statement o.k. o.k. o.k.
After Statement o.k. o.k. o.k.
If FOR EACH ROW clause is specified, then the trigger for each Row affected by the statement.
If WHEN clause is specified, the trigger fires according to the returned Boolean value.
Q.Explain how procedures and functions are called in a PL/SQL block ?
Function can be called from SQL query + explicitly as well
e.g 1)select empno,salary,fn_comm(salary)from employee;
2)commision=fn_comm(salary);
Procedure can be called from begin-end clause.
e.g.
Begin
(
proc_comm(salary);
)
end
Function is called as part of an expression.
sal := calculate_sal ('a822');
procedure is called as a PL/SQL statement
calculate_bonus ('A822');
Q.What will happen after commit statement ?
Cursor C1 is
Select empno,
ename from emp;
Begin
open C1; loop
Fetch C1 into
eno.ename;
Exit When
C1 %notfound;-----
commit;
end loop;
end;
The cursor having query as SELECT .... FOR UPDATE gets closed after COMMIT/ROLLBACK.
The cursor having query as SELECT.... does not get closed even after COMMIT/ROLLBACK.
Q.What happens if a procedure that updates a column of table X is called in a database trigger of the same table ?
Trigger will be called... Based on the event what trigger as to do. if trigger is also doing the same update statment then Mutating Table occurs. if trigger is not doing any DML statment nothing happens just Trigger will be called..
Q.Can we declare a column having number data type and its scale is larger than pricesion
ex: column_name NUMBER(10,100),
column_name NUMBAER(10,-84)
Yes,
we can declare a column with above condition.
table created successfully.
Q.The IN operator may be used if you know the exact value you want to return for at least one of the columns.
SELECT column_name FROM table_name WHERE column_name IN (value1,value2,..)
Q.What is SQL Deadlock?
Deadlock is a unique situation in a multi user system that causes two or more users to wait indefinitely for a locked resource. First user needs a resource locked by the second user and the second user needs a resource locked by the first user. To avoid dead locks, avoid using exclusive table lock and if using, use it in the same sequence and use Commit frequently to release locks.
Q.Where the Pre_defined_exceptions are stored ?
In the standard package.
Procedures, Functions & Packages ;
Q. Below is the table
city gender name
delhi male a
delhi female b
mumbai male c
mumbai female d
delhi male e
I want the o/p as follows:
male female
delhi 2 1
mumbai 1 1
Please help me in writing the query that can yield the o/p mentioned above?
select city, sum(decode(gender,'male',1,0)) Male_cnt, sum(gender,'female',1,0) female_cnt
from table_name
group by city
select a.city,a.male,b.female from
(select city,count(gender) male from city where gender='m'group by city,gender)a
join
(select city,count(gender) female from city where gender='f' group by city,gender)b
on a.city=b.city
Q.What is Sequences?
Sequences are used for generating sequence numbers without any overhead of locking. Drawback is that after generating a sequence number if the transaction is rolled back, then that sequence number is lost
Q.What are % TYPE and % ROWTYPE ? What are the advantages of using these over datatypes?
% TYPE provides the data type of a variable or a database column to that variable.
% ROWTYPE provides the record type that represents a entire row of a table or view or columns selected in the cursor.
The advantages are : I. Need not know about variable's data type
ii. If the database definition of a column in a table changes, the data type of a variable changes accordingly.
Q.What is Mutating SQL Table?
Mutating Table is a table that is currently being modified by an Insert, Update or Delete statement. Constraining Table is a table that a triggering statement might need to read either directly for a SQL statement or indirectly for a declarative Referential Integrity constraints. Pseudo Columns behaves like a column in a table but are not actually stored in the table. E.g. Currval, Nextval, Rowid, Rownum, Level etc.
Q.What is PL/SQL table ?
Objects of type TABLE are called "PL/SQL tables", which are modeled as (but not the same as) database tables, PL/SQL tables use a primary PL/SQL tables can have one column and a primary key.
Cursors
PL/SQL tables are PL/SQL?s way of providing arrays. Arrays are like tem-porary
tables in memory and thus are processed very quickly. It is impor-tant
for you to realize that they are not database tables, and DML
statements cannot be issued against them. This type of table is indexed
by a binary integer counter (it cannot be indexed by another type of
number) whose value can be referenced using the number of the index.
Remember that PL/SQL tables exist in memory only, and therefore don't
exist in any persistent way, disappearing after the session ends.
A PL/SQL TABLE DECLARATION
There are two steps in the declaration of a PL/SQL table. First, you must define the table structure using the TYPE statement. Second, once a table type is created, you then declare the actual table.
FOR EXAMPLE
DECLARE
-- Table structure definition
TYPE NameType IS TABLE OF
Customer.name_name%TYPE
INDEX BY BINARY_INTEGER;
-- Create the actual table
CnameTab NameType;
KnameTab NameType;
BEGIN
NULL; -- ...
END;
Q.In a Distributed Database System Can we execute two queries simultaneously? Justify?
Yes, Distributed database system based on 2 phase commit,one query is independent of 2 nd query so of course we can run.
Q.What are the modes of parameters that can be passed to a procedure ?
IN parameter is the default mode which acts as a constant inside calling environment.value passed in this parameter can not be changed.OUT parameter mode is used to pass value from calling environment into main block,here we can change the value.It acts as a variable inside calling environment.
INOUT parameter mode which pass value into calling environment and will get the value back in main block.
IN parameter mode uses call by reference method to pass value from formal parameter to actual parameter.
OUT & INOUT parameter mode uses call by value method to pass values.
IN,OUT,IN-OUT parameters.
Q.Name the tables where characteristics of Package, procedure and functions are stored?
User_objects, User_Source and User_error.
Q.How many types of database triggers can be specified on a table? What are they?
Insert Update Delete
Before Row o.k. o.k. o.k.
After Row o.k. o.k. o.k.
Before Statement o.k. o.k. o.k.
After Statement o.k. o.k. o.k.
If FOR EACH ROW clause is specified, then the trigger for each Row affected by the statement.
If WHEN clause is specified, the trigger fires according to the returned Boolean value.
Q.How can a function retun more than one value in oracle with proper example?
Basically as per property of function it has to return one value. So the other values can be returned from the out parameter of the function.
But its advised if you want more that one return value go for procedure however function will also yield the same result.
Q.Explain If the entire disk is corrupted how will you and what are the steps to recover the database?
if the entire disk is corrupted and no backup is there don nothing sit and relax their is no possibility of recovery ...a backup is required for restoration and for recovery redo log and archive logs.
Once if you have theses than think of recovering ..a dba should always plan for the recovery scenario depending upon the criticality of the database.oracle provides 0% data loss facilty through data guard and online backup .its dba who has to decide.
Q.What is Rollback?
Rollback causes work in the current transaction to be undone.
Q.What is a cursor for loop ?
Cursor for loop implicitly declares %ROWTYPE as loop index,opens a cursor, fetches rows of values from active set into fields in the record and closes when all the records have been processed.
eg. FOR emp_rec IN C1 LOOP
salary_total := salary_total +emp_rec sal;
END LOOP;
Q.How to sort the rows in SQL?
Sort the Rows:
SELECT column1, column2, ... FROM table_name ORDER BY columnX, columnY, ..
SELECT column1, column2, ... FROM table_name ORDER BY columnX DESC
SELECT column1, column2, ... FROM table_name ORDER BY columnX DESC, columnY ASC1.
select column1,column2,column3 from table1
where
column1>10
order by 1,3,2;
Inthis case it sorts based on the columns' position in the select query i.e. in the above query it will sort first based on column1 then on column3 and then by column2. By default the sort is in ascending order, if you want it to be in descending order, you need to specify the key word DESC in ORDER BY clause.
2.select * from emp order by eno desc;
You can sort your results based on any column in the tables because you are select all the columns.
3.select eno,ename from emp order by deptno;
This is wrong because the column deptno is not present in the select clause.
Q.What is Pragma EXECPTION_INIT? Explain the usage?
The PRAGMA EXECPTION_INIT tells the complier to associate an exception with an oracle error. To get an error message of a specific oracle error.
e.g. PRAGMA EXCEPTION_INIT (exception name, oracle error number
Q.What's the use of dyanamic sql in oracle?
Dynamic SQL enables you to write programs that reference SQL statements whose full text is not known until runtime.
Q.How we can create a table in PL/SQL block. insert records into it? is it possible by some procedure or function? please give example?
CREATE OR REPLACE PROCEDURE ddl_create_proc (p_table_name IN VARCHAR2)
AS
l_stmt VARCHAR2(200);
BEGIN
DBMS_OUTPUT.put_line('STARTING ');
l_stmt := 'create table '|| p_table_name || ' as (select * from emp )';
execute IMMEDIATE l_stmt;
DBMS_OUTPUT.put_line('end ');
EXCEPTION
WHEN OTHERS THEN
DBMS_OUTPUT.put_line('exception '||SQLERRM || 'message'||sqlcode);
END;
Q.What is a JOIN?
JOIN is the form of SELECT command that combines info from two or more tables.
Types of Joins are Simple (Equijoin & Non-Equijoin), Outer & Self join.
Equijoin returns rows from two or more tables joined together based upon a equality condition in the WHERE clause.
Non-Equijoin returns rows from two or more tables based upon a relationship other than the equality condition in the WHERE clause.
Outer Join combines two or more tables returning those rows from one table that have no direct match in the other table.
Self Join joins a table to itself as though it were two separate tables.
Q.what is the starting oracle error number?
what is meant by forward declaration in functions?
One must declare an identifier before referencing it. Once it is declared it can be referred even before defining it in the PL/SQL. This rule applies to function and procedures also.
Q.Can we declare a column having number data type and its scale is larger than pricesion
ex: column_name NUMBER(10,100),
column_name NUMBAER(10,-84)
No, you cant. May be your table might be created successfully but if you try to insert values it will shows you an error.
Numeric or Value Error
NUMBER (p,s)
p- precision, which is the total size of digits
s- scale , which represents the total number of digits that are present to the right side of the decimal.
s should be strictly less than p. If I am missing somthing. Please fill me in.
Yes,we can declare a column with above condition.table created successfully.
yes, 100 is the total size and 10 is included in 100
Q.Is it possible to use Transaction control Statements such a ROLLBACK or COMMIT in Database Trigger? Why?
It is not possible. As triggers are defined for each table, if you use COMMIT of ROLLBACK in a trigger, it affects logical transaction processing.
yes WE can use COMMIT and ROLLBACK triggers, but by using PRAGAMA AUTONAMOUS_TRANSATIONS. Now the transation treated as a autonomous tansation.
Q.What is COLUMN?
COLUMN command define column headings & format data values.
Q.SELECT statements in SQL?
SELECT column_name(s) FROM table_name
SELECT DISTINCT column_name(s) FROM table_name
SELECT column FROM table WHERE column operator value
SELECT column FROM table WHERE column LIKE pattern
SELECT column,SUM(column) FROM table GROUP BY column
SELECT column,SUM(column) FROM table GROUP BY column HAVING SUM(column) condition value
Note that single quotes around text values and numeric values should not be enclosed in quotes. Double quotes may be acceptable in some databases.
Q.What is the Delete Statements in SQL?
Delete statement in SQL is used to delete partial/all data.
Especially delete statement is useful in case of partial delete depending upon our criterias otherwise use TRUNCATE to delete whole data from table.
When delete command fires then:
1) Triggers will fire (If created on that table)
2) This will not auto commit changes made So there is one chance to rollback.
3) If u delete whole data then HWM (Highest Water Mark) will not change which gets changed in case of Truncate.
Q.What is Posting?
Posting is an event that writes Inserts, Updates & Deletes in the forms to the database but not committing these transactions to the database.
Q.Where the Pre_defined_exceptions are stored?
In the standard package.
Procedures, Functions & Packages ;
Q.What are two parts of package?
The two parts of package are PACKAGE SPECIFICATION & PACKAGE BODY. Package Specification contains declarations that are global to the packages and local to the schema.
Package Body contains actual procedures and local declaration of the procedures and cursor declarations.
Q.What are the datatypes a available in PL/SQL?
Some scalar data types such as
NUMBER,
VARCHAR2,
DATE,
CHAR,
LONG,
BOOLEAN.
Some composite data types such as RECORD & TABLE.
Q.What is an Exception? What are types of Exception?
Exception is the error handling part of PL/SQL block. The types are Predefined and user defined. Some of Predefined exceptions are.
CURSOR_ALREADY_OPEN
DUP_VAL_ON_INDEX
NO_DATA_FOUND
TOO_MANY_ROWS
INVALID_CURSOR
INVALID_NUMBER
LOGON_DENIED
NOT_LOGGED_ON
PROGRAM-ERROR
STORAGE_ERROR
TIMEOUT_ON_RESOURCE
VALUE_ERROR
ZERO_DIVIDE
OTHERS.
exception is an identifier and error handling part of pl/sql types := 1)predifined 2) user defined.
Q.Explian rowid, rownum?what are the psoducolumns we have?
ROWID - Hexa decimal number each and every row having unique.Used in searching.
ROWNUM - It is a integer number also unique for sorting Normally TOP N Analysys.
Other Psudo Column are
NEXTVAL,CURRVAL Of sequence are some exampls
psudo columns are default columns provided by oracle
Q.How to avoid using cursors? What to use instead of cursor and in what cases to do so?
Just use subquery in for clause
ex:For emprec in (select * from emp)
loop
dbms_output.put_line(emprec.empno);
end loop;
no exit statement needed
implicit open,fetch,close occurs
Q.what is the starting oracle error number?
what is meant by forward declaration in functions?
One must declare an identifier before referencing it. Once it is declared it can be referred even before defining it in the PL/SQL. This rule applies to function and procedures also
ORA-20000
Q.What are the components of a PL/SQL block?
A set of related declarations and procedural statements is called block.
DECLARE -- declaration section BEGIN -- executable statements -- main section EXCEPTION -- handling possible exceptions -- occuring in the main section END;
Q.What is difference between stored procedures and application procedures,stored function and application function?
Stored procedures are sub programs stored in the database and can be called & execute multiple times where in an application procedure is the one being used for a particular application same is the way for function
Procedure:-
Execute as a PL/SQL
statement,No RETURN clause in
the header,Can return none, one,
or many values,Can contain a RETURN
statement
Function:-Invoke as part of an
expression,Must contain a RETURN
clause in the header,Must return a single value,Must contain at least one RETURN statement
Q.What is Raise_application_error ?
Raise_application_error is a procedure of package DBMS_STANDARD which allows to issue an user_defined error messages from stored sub-program or database
trigger.
Q.What is trigger,cursor,functions in pl-sql and we need sample programs about it?
Trigger is an event driven PL/SQL block. Event may be any DML transaction.
Cursor is a stored select statement for that current session. It will not be stored in the database, it is a logical component.
Function is a set of PL/SQL statements or a PL/SQL block, which performs an operation and must return a value.
Q.How we can create a table in PL/SQL block. insert records into it??? is it possible by some procedure or function?? please give example...
CREATE OR REPLACE PROCEDURE ddl_create_proc (p_table_name IN VARCHAR2)
AS
l_stmt VARCHAR2(200);
BEGIN
DBMS_OUTPUT.put_line('STARTING ');
l_stmt := 'create table '|| p_table_name || ' as (select * from emp )';
execute IMMEDIATE l_stmt;
DBMS_OUTPUT.put_line('end ');
EXCEPTION
WHEN OTHERS THEN
DBMS_OUTPUT.put_line('exception '||SQLERRM || 'message'||sqlcode);
END;
Q.In pl/sql functions what is use of out parameter even though we have return statement.
With out parameters you can get the more than one out values in the calling program. It is recommended not to use out parameters in functions. If you need more than one out values then use procedures instead of functions.
Q.How to debug the procedure ?
You can use DBMS_OUTPUT oracle supplied package or DBMS_DEBUG pasckage.
Q.What is ref cursor?
In PL/SQL ,pointer has a datatype REF X where
REF-Reference
X-class of objects
Cursor Variables has a datatype REF-CURSOR
where Cursor Varibales are like pointers which hold the memory location of some item instead of the item itself.
Q.State the advantage and disadvantage of Cursor?
Advantage :
In pl/sql if you want perform some actions more than one records you should user these cursors only. bye using these cursors you process the query records. you can easily move the records and you can exit from procedure when you required by using cursor attributes.
disadvantage:
using implicit/explicit cursors are depended by sutiation. if the result set is les than 50 or 100 records it is better to go for implicit cursors. if the result set is large then you should use exlicit cursors. other wise it will put burdon on cpu.
Q.What is a database trigger ? Name some usages of database trigger ?
A database triggers is stored PL/SQL program unit associated with a specific database table or view. The code in the trigger defines the action the database needs to perform whenever some database manipulation (INSERT, UPDATE, DELETE) takes place.
Unlike the stored procedure and functions, which have to be called explicitly, the database triggers are fires (executed) or called implicitly whenever the table is affected by any of the above said DML operations.
Till oracle 7.0 only 12 triggers could be associated with a given table, but in higher versions of Oracle there is no such limitation. A database trigger fires with the privileges of owner not that of user
A database trigger has three parts
1. A triggering event
2. A trigger constraint (Optional)
3. Trigger action
A triggering event can be an insert, update, or delete statement or a instance shutdown or startup etc. The trigger fires automatically when any of these events occur A trigger constraint specifies a Boolean expression that must be true for the trigger to fire. This condition is specified using the WHEN clause. The trigger action is a procedure that contains the code to be executed when the trigger fires.
Database trigger is stored PL/SQL program unit associated with a specific database table. Usages are Audit data modifications, Log events transparently, Enforce complex business rules Derive column values automatically, Implement complex security authorizations. Maintain replicate tables.
Q.What are the return values of functions SQLCODE and SQLERRM ?
SQLCODE returns the latest code of the error that has occurred.
SQLERRM returns the relevant error message of the SQLCODE.
Q.How packaged procedures and functions are called from the following?
a. Stored procedure or anonymous block
b. an application program such a PRC *C, PRO* COBOL
c. SQL *PLUS
a.PACKAGE NAME.PROCEDURE NAME (parameters);
variable := PACKAGE NAME.FUNCTION NAME (arguments);
EXEC SQL EXECUTE
b.
BEGIN
PACKAGE NAME.PROCEDURE NAME (parameters)
variable := PACKAGE NAME.FUNCTION NAME (arguments);
END;
END EXEC;
c. EXECUTE PACKAGE NAME.PROCEDURE if the procedures does not have any out/in-out parameters. A function can not be called.
Q.Operators used in SELECT statements are?
= Equal
<> or != Not equal
> Greater than
< Less than
>= Greater than or equal
<= Less than or equal
BETWEEN Between an inclusive range
LIKE Search for a pattern
Q.Give the structure of the procedure ?
basically procedure has three
parts
1.variable declaretion(optional)
2.body(mandetory)
3.Exception(optional)
suppose ex
CREATE OR REPLACEPROCEDURE emp_pro( p_id IN employees.employee_id%TYPE)
IS
v_name employees.last_name%TYPE;
v_mail employees.email%TYPE;
BEGIN
SELECT last_name,email INTO v_name,v_mail FROM employees
WHERE employee_id:=p_id;
DBMS_OUTPUT.PUT_LINE('NAME:'||v_name ||'MAILID:'||v_mail);
END;
/
PROCEDURE name (parameter list.....)
is
local variable declarations
BEGIN
Executable statements.
Exception.
exception handlers
end;
Q.What is SPOOL?
spool command used for printing the out put of the sql statments in a file. Eg.
spool /tmp/sql_out.txt
select emp_name, emp_id from emp where dept='sales';
spool off;
we can see the out on /tmp/sql_out.txt file.
SPOOL command creates a print file of the report.
Q.What are advantages fo Stored Procedures
Extensibility,Modularity, Reusability, Maintainability and one time compilation.
Q.IS Stored Function Is Pre-Compiled as Stored Procedure ? If No Why
stored procedure means the pre-compiled precedure ,which is used for a specific action to be executed more than one times whenever you called from coding in the programe.
stored procedure is an important concept in the application developement in oracle.
Q.Explain the two type of Cursors ?
There are two types of cursors, Implicit Cursor and Explicit Cursor.
PL/SQL uses Implicit Cursors for queries. User defined cursors are called Explicit Cursors. They can be declared and used.
Q.What is Overloading of procedures ?
Overloading of procedure
name of the procedure is
same but the number of parameters should be different.In that case,procedure will be overloaded.
2. if the number of parameters are same in that case,data type should be different.
if the two rules are satisfied in that case procedure will be overloaded.
Q.What is PL/SQL ?
PL/SQL is a procedural language that has both interactive SQL and procedural programming language constructs such as iteration, conditional branching.
Q.What are the PL/SQL Statements used in cursor processing ?
DECLARE CURSOR cursor name, OPEN cursor name, FETCH cursor name INTO or Record types, CLOSE cursor name.
Q.What is Set Transaction?
Set Transaction is to establish properties for the current transaction.
Q.What is Character Functions?
Character Functions are INITCAP, UPPER, LOWER, SUBSTR & LENGTH. Additional functions are GREATEST & LEAST. Group Functions returns results based upon groups of rows rather than one result per row, use group functions. They are AVG, COUNT, MAX, MIN & SUM.
Q.What is an Exception ? What are types of Exception?
Exception is the error handling part of PL/SQL block. The types are Predefined and user defined. Some of Predefined exceptions are.
CURSOR_ALREADY_OPEN
DUP_VAL_ON_INDEX
NO_DATA_FOUND
TOO_MANY_ROWS
INVALID_CURSOR
INVALID_NUMBER
LOGON_DENIED
NOT_LOGGED_ON
PROGRAM-ERROR
STORAGE_ERROR
TIMEOUT_ON_RESOURCE
VALUE_ERROR
ZERO_DIVIDE
OTHERS.
Q.Is it possible to use Transaction control Statements such a ROLLBACK or COMMIT in Database Trigger? Why?
It is not possible. As triggers are defined for each table, if you use COMMIT of ROLLBACK in a trigger, it affects logical transaction processing.
yes WE can use COMMIT and ROLLBACK triggers, but by using PRAGAMA AUTONAMOUS_TRANSATIONS. Now the transation treated as a autonomous tansation.
Q.What is Multiple columns?
Multiple columns can be returned from a Nested Subquery.
Q.What is Savepoint?
Savepoint is a point within a particular transaction to which you may rollback without rolling back the entire transaction.
