I apologize, but this is kind of a two part question.
I\'m extremely new to SQL and am trying to develop a time clock application for the small office that I work in
As others have suggested that you should look into MERGE statement but nobody provided a solution using it I'm adding my own answer with this particular TSQL construct. I bet you'll like it.
Your code has a typo in your if statement in not exists(select...) part. Inner select statement has only one where condition while UserName condition is excluded from the not exists due to invalid brace completion. In any case you cave too many closing braces.
I assume this based on the fact that you're using two where conditions in update statement later on in your code.
Let's continue to my answer...
MERGE statement is a beautiful TSQL gem very well suited for "insert or update" situations. In your case it would look similar to the following code. Take into consideration that I'm declaring variables what are likely stored procedure parameters (I suspect).
declare @clockDate date = '08/10/2012';
declare @userName = 'test';
merge Clock as target
using (select @clockDate, @userName) as source (ClockDate, UserName)
on (target.ClockDate = source.ClockDate and target.UserName = source.UserName)
when matched then
update
set BreakOut = getdate()
when not matched then
insert (ClockDate, UserName, BreakOut)
values (getdate(), source.UserName, getdate());