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Answer Posted / sachin fulari
Brief about Cursors
-------------------
Every SQL statement executed by Oracle has a Private SQL
area that contains info about SQL statement and the set of
data returned.
In PL/SQL, a cursor is a name assigned to a specific
private SQL area of a specific SQL Statement.
There can be either, Static Cursor whose SQL statements is
determined at compile time, or Dynamic Cursor, whose SQL
statement is determined at runtime.
Note: Dynamic Cursors are implemented using Oracle built in
package DBMS_SQL.
Implicit Cursors:
----------------
Any SQL statement that is executed directly or in an PL/SQL
block i.e. execution section or in exception section,
during which it is associated with a work area in memory of
oracle (SGA). This is done using implicit cursor by Oracle.
We do not need to declare implicit cursor hence not be
opened, fetched and closed.
Explicit Cursors:
-----------------
They are the SELECT statement that is declared explicitly
in the declaration section of current block or in a package
specification.
Further we can use open, fetch and close in execution
section or exception section of the block or program to
utilize declared cursor.
To use an explicit cursor we need to declare it in
declaration section of block or package specification.
There are three sub types of explicit cursors:
* Simple Cursor (without parameter)
CURSOR emp_cur IS
SELECT emp_id
FROM emp;
* Parameterized Cursor - That accepts arguments
CURSOR emp_cur (dept_in [IN] NUMBER) IS
SELECT emp_id
FROM emp
WHERE dept = dept_in ;
* Returning Cursor - A cursor header that contains
a return clause
CURSOR emp_cur (dept_in [IN] NUMBER) IS
RETURN emp%ROWTYPE
SELECT *
FROM emp;
Hope so, above paragraphs explain cursors very well and in
details.
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