SQL のお勉強 - 型の自動変換と等価性について
mysql> select * from (select '' as t) as t1 where t=0; +---+ | t | +---+ | | +---+ 1 row in set (0.00 sec) mysql> select * from (select '' as t) as t1 where t='0'; Empty set (0.00 sec)
mysql> select * from (select '' as t) as t1 where t=0; +---+ | t | +---+ | | +---+ 1 row in set (0.00 sec) mysql> select * from (select '' as t) as t1 where t='0'; Empty set (0.00 sec)