8 SQL Server Trigger interview questions with answers.
Triggers are like stored procedures which get executed in response to DML statements like insert, delete and update on certain tables.
What are the types on Triggers?
Its InsteadOf trigger and For Trigger.
What is the difference between For Trigger and After trigger?
What is the difference between InsteadOf and After/For trigger?
InsteadOf trigger will be fired on behalf of DML statements whereas After trigger will be fired after DML statements.
What is the use of InsteadOf and After Trigger?
InsteadOf – > Override Insert, Update or Delete operation.
Let’s have a scenario, we have a table in production but in order to fulfill change requirement of one of the client we need to change its structure. Problem with this kind of change is all the existing insert, update and delete procedure should get changed which again can be a big overhead because in enterprise applications sometimes it might not be possible to know all the locations where these DML statements have been fired. With the help of InsteadOf trigger we can just replace existing DML queries with something else.
After Trigger -> Logging.
Let’s say you have a scenario where you want to store flags whenever Table data is modified. After trigger comes to handy then.
Is it possible to create trigger on views?
Yes, only InsteadOf trigger.
How many triggers are possible per table?
One InsteadOfTrigger and any After Triggers.
When multiple after triggers are attached to sql table, how to control the order of execution?
Using sp_settriggerorder procedure.
All the above 8 SQL Server trigger interview questions are provided by questpond.com
Below is a nice SQL Server interview question video on triggers.