Tuesday, April 12, 2011


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.

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.

Declarative part, Executable part and Execption part.


What are the datatypes a available in PL/SQL ?

Some scalar data types such as
Some composite data types such as RECORD & TABLE.

 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:
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.

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.

What is PL/SQL table ?

Objects of type TABLE are called "PL/SQL tables", which are modelled 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.

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.

Explain the two type of Cursors ?

There are two types of cursors, Implict Cursor and Explicit Cursor.
PL/SQL uses Implict Cursors for queries.
User defined cursors are called Explicit Cursors. They can be declared and used.

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.

What are the cursor attributes used in PL/SQL ?

%ISOPEN - to check whether cursor is open or not
% ROWCOUNT - number of rows featched/updated/deleted.
% FOUND - to check whether cursor has fetched any row. True if rows are featched.
% NOT FOUND - to check whether cursor has featched any row. True if no rows are featched.
These attributes are proceded with SQL for Implict Cursors and with Cursor name for Explict Cursors.

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;

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.

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)

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