Oracle triggers if updating performance
These 'T4' & 'T5' tables are in database 'B' therefore a db_link is used in for inserting the data in T4 & T5 tables. ( Even I used AUTONOMOUS TRANSAXTION in this trigger but performance has not improoved as desired) March 30, 2007 - pm UTC I can improve this process.
lose database B, drop table t2, t4 and t5 - consolidate this all.
How can we make sure that it is fired only once for each row in an update statement other than using "After trigger for statement"? ONLY the after for each row can look at a "stable" value in the :new record.
So, if you doing data validation (eg: this column must be between 1 and 30 when this condition is true), you should do that in an AFTER trigger because the BEFORE triggers may change the value on you (and since BEFORE triggers fire in SOME RANDOM order -- you cannot be assured that your BEFORE trigger fires before or after some other BEFORE trigger) So, use BEFORE FOR EACH row when you need to WRITE to the :new record use AFTER FOR EACH row triggers when you want to VALIDATE the final values in the :new record That entire referenced thread was the proof that you cannot be sure the trigger is fired only once for each row! Addenda 2017 ============ The statement "and since BEFORE triggers fire in SOME RANDOM order -- you cannot be assured that your BEFORE trigger fires before or after some other BEFORE trigger" is no longer true in recent versions of Oracle, the FOLLOWS clause allows you to define a firing order.
eg:- I am trying to insert a varchar value into a deptno [number], just to see if trigger fires , and it does, even after going to when others section in exception Why is that so and can I force trigger to fire only on success?
CREATE TABLE DEPT ( DEPTNO NUMBER(5), DNAME VARCHAR2(20 BYTE), LOC VARCHAR2(20 BYTE) ) CREATE TABLE LOG_TABLE ( MESSAGE VARCHAR2(2000 BYTE), TIME_STMP DATE DEFAULT sysdate ) --Trigger on dept table: CREATE OR REPLACE TRIGGER DEPT_TRG BEFORE DELETE OR INSERT OR UPDATE ON DEPT FOR EACH ROW begin insert into log_table(message) values('DML on DEPT Table '); end; / --function for DML on dept create or replace function dml_dept return integer is begin insert into dept(deptno) values('testing trigger behaviour'); exception when others then return -1; end; December 14, 2005 - pm UTC the "exception" is not happening until it happens - the BEFORE trigger you have fires well before the first byte of data is touched.
Asked: November 29, 2004 - pm UTC Answered by: Connor Mc Donald - Last updated: August 04, 2017 - am UTC Category: Database - Version: 22.214.171.124 Viewed 10K times!
This question is Tom, Most of the times it appear that either before or after row trigger can be used to serve the purpose in real world applications.
will the process revisit the rollback segment perhaps ?
TIA (as always) Hi Tom Kindly help me out 1) Trigger T1 is created by user U1 against a table T1 and also the user U1 has granted full permission to the user U2.
Under what circumstances before and after trigger needs to be used.
As per this note: A trigger can be fired more than once for the same row update from one sql statement. you can have many before triggers -- each modifying the :new values.
Now, When user u1 try to insert/update/delete from table T1, Should Trigger fire or not? Krishna Kumar insert into t1 values (1); TRG2 TRG1 1 row created. Regards Michel constraints technically are validated AFTER the statement executes - it is not really defined whether a trigger will or will not fire (and if you have logic that depends on such intricate ordering, we have a really big logic problem) September 07, 2006 - am UTC not really, it is just that "it is more complex than can be simply stated as a sequence of operations" a simple check constraint - sure but a constraint that needs to look "across rows" like a primary key or foreign key - they are conceptually done AFTERWARDS. I no longer think that a list of modified blocks is necessary; all it takes it's just a counter of violations (index collisions) maintained as the DML executes. Emrick blog (very interesting) and thank to "A Reader" for the "exact link to the pk=pk 1 topic", also to Eric's blog :) Tom, it's very helpful for me. I am updating one table with after I/U/D for each row... So I need to track which columns are being updated.Tags: Adult Dating, affair dating, sex dating