mySQL: Multiple COUNT()s based on differing criteria

Question

Alright, so what I\'m trying to do is perform different COUNT()s on the same table based on different criteria without nested queries (efficiency) or subqueries (so it can be ma

Answer 1

You're using MySQL, so you can take advantage of its feature that a boolean expression evaluates to 0 for false and 1 for true. The SUM() of 1's is equal to a COUNT() where the expression is true.

SELECT SUM( date_column < '2009-08-21' ) AS prior_to_date,
       SUM( date_column > '2009-08-21' ) AS after_date
FROM MyTable;

PS: Don't try this on other brands of database that uphold the SQL standard behavior, i.e. a boolean expression yields a boolean, not a 0 or 1 integer.