Following few lines shows a test case creating a table, an index, and then populating a row in the table.REDO records and change vectors If a row is modified by a SQL statement, Oracle Database generates redo records describing that change.
CREATE or REPLACE TRIGGER emp_after_insert AFTER INSERT ON emp FOR EACH ROW DECLARE BEGIN insert into emp_backup values (:new.empid, :new.fname, :new.lname); DBMS_OUTPUT.
PUT_LINE('Record successfully inserted into emp_backup table'); END; Second Problem: We want o update a record in the ’emp_backup’ table if a corresponding record is updated in the ’emp’ table.
Jared Still came up with a fine method to understand this issue measuring redo/undo size.
We will explore the same questions with redo log dump method in this blog entry.
Vishwanath Dalvi is a gifted engineer and tech enthusiast. When not hacking around or supporting the open source community, he is trying to overcome his phobia of dogs.
Cross table update (also known as correlated update, or multiple table update) in Oracle uses non-standard SQL syntax format (non ANSI standard) to update rows in another table. Update data in table A based on two or more common columns in table B.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.With this one, I set out to demonstrate the advantages of PARALLEL DML, didn't find what I thought I would, and ended up testing 8 different techniques to find out how they differed. The methods covered include both PL/SQL and SQL approaches.(or) Does RDBMS engine have an optimization skipping the update, as value of that column is not changing?This was the essence of a question asked in Oracle-l list and I think, it is a good topic for further discussion.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.