The SQL COUNT function is used to count the number of rows returned in a SELECT statement.

What does count 1 mean SQL?

COUNT(1) is basically just counting a constant value 1 column for each row. As other users here have said, it’s the same as COUNT(0) or COUNT(42) . Any non- NULL value will suffice.

What is difference count * and count 1?

There is no difference. It is very common perception that the Count(1) perform better compared to Count(), however it is not the case. If you test by looking at the execution plan, you will see same action being performed by both the commands and same number of rows being scanned.