Because the trigger uses the clause, it might be executed multiple times, such as when updating or deleting multiple rows.You might omit this clause if you just want to record the fact that the operation occurred, but not examine the data for each row.I need to create a SQL Server trigger that will execute when a column value is updated to a specific value. In this tip, we show you how to write T-SQL statements that will create a SQL Server trigger that will execute after we update a column value to a specific value.
Using the clause WHERE Order Status='Approved' by itself to limit the rows updated will actually result in all rows with an Order Status value of Approved being updated at the same time.
To test the trigger, we will execute a T-SQL UPDATE statement to set the Order Status value to "Approved" for the first row in the table (pk ID = 1).
create table Employee( 2 ID VARCHAR2(4 BYTE) NOT NULL, 3 First_Name VARCHAR2(10 BYTE), 4 Last_Name VARCHAR2(10 BYTE), 5 Start_Date DATE, 6 End_Date DATE, 7 Salary Number(8,2), 8 City VARCHAR2(10 BYTE), 9 Description VARCHAR2(15 BYTE) 10 ) 11 / Table created.
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.
For example, a table and a trigger can have the same name (however, to avoid confusion, this is not recommended).
A trigger is fired based on a triggering statement, which specifies: statement might include a list of columns. Deptno) AS Amp_list_ Emplist FROM Dept_tab d; The statement level triggers are useful for performing validation checks for the entire statement. It works, but it won't tell you if the value changed, only that the column is being updated (even if the update doesn't change the value).Many applications update all of the columns in a table -- setting them to their old value, rather then trying to figure out exactly which columns have been updated by the client. create or replace trigger test_trigger 2 after update of x,y on test 3 for each row 4 begin 5 if updating( 'X' ) then 6 dbms_output.put_line( 'X is being updated' ); 7 end if; 8 9 if updating( 'Y' ) then 10 dbms_output.put_line( 'Y is being updated' ); 11 end if; 12 end; 13 / Trigger created.But this is recursive and I don't want that, causes deadlocks and other weirdness. I see that INSTEAD OF triggers are non-recursive, but if I do that do I have to check every other column in the Inserted to see if it got updated or will SQL Server handle that for me? @ypercubeᵀᴹ not a bad idea, but it won't work if the user expressly tries to update [Last Updated] along with the other columns will it? When the user updates the column manually in takes their update, and doesn't cause recursion when they don't. I've also seen this done using the SET MAXRECURSION command but since this is a database level setting, I usually prefer not to mess with it too much on a single operation. As @ypercubeᵀᴹ pointed out in the comments, How do I add a “last updated” column in a SQL Server 2008 R2 table? Checking to see if the column has been updated just skips the logic and works the way I expect it to. Last Updated = GETDATE() 90 FROM Contact ct WHERE ...Once the trigger is created, entering the following SQL statement: A trigger is either a stored PL/SQL block or a PL/SQL, C, or Java procedure associated with a table, view, schema, or the database itself.