See Re: Which statement is 'Better' Thread #1048319 Message #1335280

>Thanks for the answer Sergey.
>
>>An EXISTS subquery doesn't return any data so there's no reason to list any columns in it.
>>
>>>That conflicts with the rule-of-thumb: "Never use * when selecting, always specify the fields".
>>>I know you are a very smart man, so I am wondering why you would do this.
>>>Does it change performance or just reduce typing?
>>>
>>>Einar
>>>
>>>>I use '*' in subquery because the field list is irrelevant in this case.
>>>>

IF NOT EXISTS(SELECT * FROM [MyTable] WHERE [PK] = @PK) ...

>>>>