“SELECT TOP 1 1” VS “IF EXISTS(SELECT 1”

Question

I have some .NET code that checks for the existence of a SQL record at a moderately-high interval. I am looking to make this check as \"cheap\" as possible.

I\'m wo

Answer 1

I'd recommend IF EXISTS(SELECT * ...), unless this is actually causing a performance issue. It expresses the intent of the query in a much better understood fashion than alternatives.

I'd avoid COUNT(*) (as in the current answers) unless you actually need the count of rows from the table.

If you want the "efficiency" of checking the rowcount from the result, I'd probably go for:

select 1 where exists(select * from BigTable where SomeColumn=200)

Which produces the same result set as your second query (either 0 or 1 row)