SELECT 1 VS Select *

Connor Cunningham has a great explanation of the difference between using SELECT 1 versus SELECT * in an EXISTS clause.  I’d like to add that I’m assuming that the same rule would apply to SELECT count(*) and SELECT count(1).

SQL Query Optimizer would expand * into the column list and then figure out that none of them are needed.  So theoretically, SELECT count(1) would be a little faster in putting the plan together, but would run at the same speed and have the same IOs as SELECT count(*).

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