Jay Robinson shows that wrapping identifiers with brackets does nothing for performance:
Anyway, this obsession had me thinking – does wrapping identifiers in square brackets save SQL Server any time? Does it say to the optimizer, “Hey, I PROMISE this whole thing inside these square brackets is an identifier. Cross my heart.” And the optimizer takes your code at its word and doesn’t look through its list of reserved keywords for one that matches AccountCreateDate or address_line_2?
The answer is… no. Throwing every identifier into square brackets doesn’t speed it up at all. Here’s the test:
Read on for the test.