Most frequently Asked Oracle Pl/SQL Interview Questions and Answers for freshers and experienced pdf free download
1. 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.
2. 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
3. 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.
4. In a Distributed Database System Can we execute two queries simultaneously? Justify?
s Distributed database system based on 2 phase commit,one query is independent of 2 nd query so of course we can run.
5. 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;
6. 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
7. State the difference between implict and explict cursors?
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.
Implicit cursors are used for single row query whereas explicit cursor is used for multiple row query
8. 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.
9. How can a function retun more than one value in oracle with proper example?
yes we can use objects, arrays to return more than one value
10. 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.
11. What is the basic structure of PL/SQL?
PL/SQL uses block structure as its basic structure. Anonymous blocks or nested blocks can be used in PL/SQL.
12. 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;
13. 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.
14. 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.
15. What is difference between % ROWTYPE and TYPE RECORD?
% ROWTYPE is to be used whenever query returns a entire row of a table or view.
TYPE rec RECORD is to be used whenever query returns columns of different
table or views and variables.
E.g. TYPE r_emp is RECORD (eno emp.empno% type,ename emp ename %type);
e_rec emp% ROWTYPE
cursor c1 is select empno,deptno from emp;
e_rec c1 %ROWTYPE.
One more point : When we have a variable of typer RECORD we have declare additional variables but with %rowtype, we can only have the fields that are present in the table
16. 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 yuo
17. 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
18. 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.
yes, 100 is the total size and 10 is included in 100
19. 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.
20. Explain the usage of WHERE CURRENT OF clause in cursors?
WHERE CURRENT OF clause in an UPDATE,DELETE statement refers to the latest row fetched from a cursor. Database Triggers .
More Oracle Pl/SQL Interview Questions : Click Here
1. 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.
2. 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
3. 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.
4. In a Distributed Database System Can we execute two queries simultaneously? Justify?
s Distributed database system based on 2 phase commit,one query is independent of 2 nd query so of course we can run.
5. 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;
6. 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
7. State the difference between implict and explict cursors?
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.
Implicit cursors are used for single row query whereas explicit cursor is used for multiple row query
8. 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.
9. How can a function retun more than one value in oracle with proper example?
yes we can use objects, arrays to return more than one value
10. 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.
11. What is the basic structure of PL/SQL?
PL/SQL uses block structure as its basic structure. Anonymous blocks or nested blocks can be used in PL/SQL.
12. 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;
13. 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.
14. 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.
15. What is difference between % ROWTYPE and TYPE RECORD?
% ROWTYPE is to be used whenever query returns a entire row of a table or view.
TYPE rec RECORD is to be used whenever query returns columns of different
table or views and variables.
E.g. TYPE r_emp is RECORD (eno emp.empno% type,ename emp ename %type);
e_rec emp% ROWTYPE
cursor c1 is select empno,deptno from emp;
e_rec c1 %ROWTYPE.
One more point : When we have a variable of typer RECORD we have declare additional variables but with %rowtype, we can only have the fields that are present in the table
16. 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 yuo
17. 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
18. 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.
yes, 100 is the total size and 10 is included in 100
19. 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.
20. Explain the usage of WHERE CURRENT OF clause in cursors?
WHERE CURRENT OF clause in an UPDATE,DELETE statement refers to the latest row fetched from a cursor. Database Triggers .
More Oracle Pl/SQL Interview Questions : Click Here
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