SQL: How to properly check if a record exists

Question

While reading some SQL Tuning-related documentation, I found this:

SELECT COUNT(*) :

• Counts the number of rows.
• Often is improper

Answer 1

You can use:

SELECT 1 FROM MyTable WHERE... LIMIT 1

Use select 1 to prevent the checking of unnecessary fields.

Use LIMIT 1 to prevent the checking of unnecessary rows.