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instead of insert

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Topic

amitbarkai
Starting Member

19 Posts

Posted - 2010-05-27 : 05:07:13

Hey All

i am tring to figure out few things about triggers
let say i want to validate my data before inserting in to my table
for that we have the instead of insert

what i could find is a good example that
validate a single filed on insert
of combination of 2 field

can anyone give my an example
that prevent the insert if a field equals to value

thanks

asgast
Posting Yak Master

149 Posts

Posted - 2010-05-27 : 06:36:49

if you want to just validate data before inserting, try using check constraint

for examples on triggers try looking into BOL http://msdn.microsoft.com/en-us/library/ms189799%28SQL.90%29.aspx

Kristen
Test

22859 Posts

Posted - 2010-05-27 : 09:49:03

Validate Data can be done in AFTER trigger (it can rollback the changed data) and AFTER triggers are a WHOLE PILE easier to write & maintain.

But I see Triggers as being a long stop. Better to have caught the validation issues before then, if possible, so you can present user-friendly messages / options to the user. A trigger is going to raise an error that will abort the transaction - and is not likely to be handled very gracefully by your application.

OTOH a Stored Procedure, or some "middle-tier", could return an error code, and a suitable user-friendly message, which the application could easily use to guide the User

DonAtWork
Master Smack Fu Yak Hacker

2167 Posts

Posted - 2010-05-27 : 09:49:27

You could also have the business layer of your application validate any data passed to your data layer.

http://weblogs.sqlteam.com/jeffs/archive/2008/05/13/question-needed-not-answer.aspx
How to ask: http://weblogs.sqlteam.com/brettk/archive/2005/05/25/5276.aspx
For ultra basic questions, follow these links.
http://www.sql-tutorial.net/
http://www.firstsql.com/tutor.htm
http://www.w3schools.com/sql/default.asp

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