Should I COUNT(*) or not?

Question

I know it\'s generally a bad idea to do queries like this:

SELECT * FROM `group_relations`

But when I just want the count, should I go for this

Answer 1

An asterisk in COUNT has no bearing with asterisk for selecting all fields of table. It's pure rubbish to say that COUNT(*) is slower than COUNT(field)

I intuit that select COUNT(*) is faster than select COUNT(field). If the RDBMS detected that you specify "*" on COUNT instead of field, it doesn't need to evaluate anything to increment count. Whereas if you specify field on COUNT, the RDBMS will always evaluate if your field is null or not to count it.

But if your field is nullable, specify the field in COUNT.