i have 2 questions??
1.can we use insert,delete inside user defined function(i tried myself it showing error 'side-effecting operator 'DELETE' within a function.')?
if not why?
No you can't with the slight exception of manipulating a @Table variable. the reason is in SQL server, FUNCTIONS are a streamlined form of a stored procedure, and can only perform READ operations (ie SELECT.
it cannot insert/update/delete to any table or #temp table either. if you need to do that, you have to use a stored proc
2.what is isolation in sql server? where it is used ?
MS can probably describe it better than me:http://msdn.microsoft.com/en-us/library/ms173763.aspx?ppud=4
basically, the isolation level decides what rules are in place when two people are using the same data at the same time: so if i'm updating some data, lets say your lunch schedule, for 12:00 to 1:00 , do you see the data as it existed how it was before i finish updating(still 12:00, or does your request have to wait you have to wait till i'm done committing the transaction before you can see the data.
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