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In SQL, i know the use of select * which basically means selecting all rows but what does count(*) do and how does it work?

shashank agrawal
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    https://dev.mysql.com/doc/refman/8.0/en/aggregate-functions.html#function_count – Andy Refuerzo Oct 09 '22 at 08:39
  • select * which basically means selecting all rows - No it means select all columns the number of rows returned is determined by WHERE conditions and JOIN conditions. – P.Salmon Oct 09 '22 at 09:40

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This is fairly well documented here https://dev.mysql.com/doc/refman/8.0/en/aggregate-functions.html#function_count

Returns a count of the number of non-NULL values of expr in the rows retrieved by a SELECT statement. The result is a BIGINT value.

If there are no matching rows, COUNT() returns 0. COUNT(NULL) returns 0.

Andy Refuerzo
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