New to T-SQL Conditional calcualtion

[vmon]

How would I do something like this in a T-SQL statement?
I have only done a little SQL and it was in Access.

I want to update a column in a temporary table called BegBalance to AmountSent if PreviousCollected is Null otherwise calcualte it as [Amount_Sent]-[PreviousCollected]-[PreviousAdjusted]

In Access I did it like this

BegBalance: IIf(IsNull([PreviousCollected]),[Amount_Sent],[Amount_Sent]-[PreviousCollected]-[PreviousAdjusted])

thanks,
vmon

 

[SQLSister]

Read in Books Online about the Case statement, it is SQL Server's replacement for the IIF command in Access

 

[ClaireHCM]

The folowing is query idea is from SQLsister's reply!

update BegBalance set previouscollected=(case when PreviousCollected is null then Amount_Sent
else [Amount_Sent]-[PreviousCollected]-[PreviousAdjusted] end)