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PL/SQL Tutorial (Examples) - page 4 (go to page 1) CURSORS Cursor is a work area in pl/sql which is used by sql server used to store the result of a query. Cursors are of 2 types: implicit and explicit.......implicit cursors are created by oracle engine itself while explicit cursors are created by the users......cursors are generally used in such a case when a query returns more than one rows....normal pl/sql returning more than one rows givens error but using cursor this limitation can be avoided...cursors are used.... at first a cursor consisting of query result is created in server..the cursor is transferred to the client where again cursor is created and hence the result is displayed......In PL/SQL, the context area is controlled by Cursor.A cursor contains information on a select statement and the rows of data accessed by it.Examples (these use the cursor declaration examples above): Once a cursor has been opened, it can be manipulated with the statements described here.When an SQL statement is processed, Oracle creates a memory area known as context area. It contains all information needed for processing the statement.
Cursors can be made into use using cursor for loop and fetch statement..will see the corresponding examples...It will return an error if there no data is selected.What I love about writing SQL Tuning articles is that I very rarely end up publishing the findings I set out to achieve. We have a table containing years worth of data, most of which is static; we are updating selected rows that were recently inserted and are still volatile. For the purposes of the test, we will assume that the target table of the update is arbitrarily large, and we want to avoid things like full-scans and index rebuilds.For example: When you execute the SQL statements like INSERT, UPDATE, DELETE then the cursor attributes tell whether any rows are affected and how many have been affected.If you run a SELECT INTO statement in PL/SQL block, the implicit cursor attribute can be used to find out whether any row has been returned by the SELECT statement.
This provides an efficient way to return large row sets from functions. As usual, this gives flexibility so the query plan can vary from one run to the next (see Section 39.10.2), and it also means that variable substitution is not done on the command string.