Eugene Elutin (10/15/2012)
... There wouldn't be any overhead since the DB isn't querying anything to get the value of [a].
...
Except the fact that this will lead to full table (or, if you have an index on this column, then Index) scan...
Since there's no other where clause, it has to scan anyway. If there was a sargable predicate, SQL would seek for that.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability