SQL trigger, check if certain value was entered

Anonymous User 2543 17-Apr-2013

Hi Expert!

INSERT INTO table_name (column1, column2, column3,...)

VALUES (value1, value2, value3,...)

Now what to check:

If inserted value1 = null, change it to 0

How to do it via trigger? I googled for examples and I have never ever done a trigger, so it is rather confusing.

So far got only this:

CREATE TRIGGER testTrigger

ON myTable

AFTER INSERT, UPDATE, DELETE

Advance Thanks!

mssql server

Updated on 17-Apr-2013

I am a content writter !

Can you answer this question?

Answer

17-Apr-2013

Hi Jacob!

You can add default value . This is how it's done for a new column. For existing one you should add constraint. Check Update 2


ALTER TABLE table_name 
ADD column1 int NOT NULL DEFAULT(0)
Add column, with default value, to existing table in SQL Server

UPDATE:

To set default value, you should update NULL values at first.

UPDATE table_name 
SET column1 = 0
WHERE column1 IS NULL
UPDATE 2:

Try adding constraint

ALTER TABLE table_name 
ADD CONSTRAINT DF_column1 DEFAULT 0 FOR column1

17-Apr-2013

Hi Jacob!

You can try another way as following

You could write this in the trigger:

UPDATE T SET value1 =0

FROM table_name T

JOIN INSERTED I

ON T.<id>=I.<id>

WHERE I.value1 is null

INSERTED table which is accessible only within trigger will store the values that have inserted..

forum