So sql, ...count(*)... and ...count(id)... what is the difference?

I

iOS Dav2016-08-09 22:00:51

SQL

iOS Dav, 2016-08-09 22:00:51

In some sql queries they write ...count(*)... and in some ...count(id)... so what's the difference?

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Alexey Nemiro, 2016-08-09
@Aidosss

SELECT COUNT(*) FROM - iterate over all rows.
SELECT COUNT(id) FROM - iterate over all rows in which the specified field (in this case id ) has a value other than NULL .
What to use is a matter of performance and needs. In the case of primary key , it's more of a performance issue, which will depend on the specific DBMS.