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When the Fetch clause is used with a cursor having a FOR UPDATE clause, the PL/SQL unit fails when we try to open the cursor with an ORA-02014: cannot select FOR UPDATE from view with DISTINCT, GROUP BY, etc. The error description shows that the internal mechanism for the Fetch clause uses either a DISTINCT or a GROUP BY clause which is not permitted alongside the FOR UPDATE clause.In this scenario, the cursor result set can be limited using the traditional When we associate a SELECT statement with more than one table joined together to a cursor with a FOR UPDATE clause, we end up locking all the tables in the FROM clause of the SELECT statement, where we just need to lock a single table for our purpose.This clause becomes meaningless if we use a single table SELECT clause as the minimum Oracle has provided us with the WHERE CURRENT OF clause for both DELETE and UPDATE statements inside a cursor’s range to make changes to the last fetched row(s) from the cursor with an ease.When we want to update or delete the cursor fetched row(s) from the database, we don’t have to form In the below code listing, the employees joined before the year 2000 are archived and during the cursor process, no other session is permitted to make any changes to those employees using the FOR UPDATE clause.23 COMMIT; 24 END; 25 / PL/SQL procedure successfully completed.DECLARE CURSOR c1 IS SELECT course_number, ROWID AS RID FROM courses_tbl FOR UPDATE; begin FOR a Course IN c1 LOOP UPDATE courses_tbl SET course_number = a Course.course_number 1 WHERE CURRENT OF c1; UPDATE courses_tbl SET course_number = a Course.course_number 1 WHERE ROWID = a Course.SQL select * from Employee 2 / ID FIRST_NAME LAST_NAME START_DAT END_DATE SALARY CITY DESCRIPTION ---- -------------------- -------------------- --------- --------- ---------- ---------- --------------- 01 Jason Martin 25-JUL-96 25-JUL-06 1234.56 Toronto Programmer 02 Alison Mathews 21-MAR-76 21-FEB-86 6661.78 Vancouver Tester 03 James Smith 12-DEC-78 15-MAR-90 6544.78 Vancouver Tester 04 Celia Rice 24-OCT-82 21-APR-99 2344.78 Vancouver Manager 05 Robert Black 15-JAN-84 08-AUG-98 2334.78 Vancouver Tester 06 Linda Green 30-JUL-87 04-JAN-96 4322.78 New York Tester 07 David Larry 31-DEC-90 12-FEB-98 7897.78 New York Manager 08 James Cat 17-SEP-96 15-APR-02 1232.78 Vancouver Tester 8 rows selected.
This is a complete book on PL/SQL with everything you need to know to write efficient and complex PL/SQL code.The WHERE CURRENT OF clause in an UPDATE or DELETE statement states that the most recent row fetched from the table should be updated or deleted.We must declare the cursor with the FOR UPDATE clause to use this feature.Oracle defines an execution cycle to execute an SQL statement and associates a cursor with it.
The following illustration shows the execution cycle of an explicit cursor: Let’s examine each step in detail.
RID end loop; end; When we want to update or delete the cursor fetched row(s) from the database, we don’t have to form a UPDATE or a DELETE statement with a primary key mapping in its WHERE clause, instead, the WHERE CURRENT OF clause comes in handy.