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Answer Posted / tripti gour
In order to process a sql statements oracle will allocate an
area of memory known as the context area. The context area
contains information necessary to complete the processing,
including the number of rows processed by the select
statement, a pointer to the parsed representation of the
statement, and in the case of a query, the active set,
which is the set of rows returned by the query.
A cursor is a handle or pointer to the context area.
Sql cursor attributes are:
1. SQL%ROWCOUNT: number of rows affected by the most recent
sql statement (an integer value).
2. SQL%FOUND: Boolean attribute that evaluates to TRUE if
the most recent SQL statement affects one or more rows.
3. SQL%NOTFOUND: Boolean attribute that evaluates to true if
the most recent SQL statement does not affects any rows.
4. SQL%ISOPEN: always evaluates to false because pl/sql
closes implicit cursors immediately after they are executed.
Cursor Types:
1. Implicit cursor
2. Explicit Cursor
3. REF cursor
4. Parametrized cursor
5. FOR LOOP Cursor
Implicit cursor:
a.Are opened implicitly by oracle whenever a DML or select
statement is executed.
b.Opened, fetched, closes internally.
c.Un-named cursors
d.Attributes: sql%isopen, sql%found, sql%notfound, sql%rowcount.
Explicit cursor
•Are declared and opened explicitly by developers to
manipulate multiple rows returned by queries one by one.
•Manually we have to declare, open, fetch, and close it.
•Name given to a context area.
•Attributes: cur_name%isopen, cur_name%found,
ur_name%notfound, cur_name%rowcount.
REF CURSOR EXAMPLE
declare
type t1 is ref cursor;
v1 t1;
begin
open v1 for select * from inv;
open v1 for select * from inv2;
end;
Parameterized cursor:
We can pass parameters for cursor as like procedures and
functions.
Syntax: cursor cursor_name[parameter_name datatype] is
select statement;
the advantage of parameterized cursor is, a single cursor
can be opened and closed several times in a block, returning
different active set in each occasion.
Note: formal parameters should not be mentioned with data type
Thanks,
Tripti
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