加法、减法、乘法和除法运算符如何与以 MySQL 字符串表示的日期配合使用?
mysqlmysqli database
此类计算可能会导致不可预测的结果，因为当日期以 MySQL 字符串表示时，MySQL 会尝试通过仅取第一个出现的字符串对字符串执行数字运算。以下示例将对此进行说明 −
mysql> select '2017-10-17' + 20; +-------------------+ | '2017-10-17' + 20 | +-------------------+ | 2037 | +-------------------+ 1 row in set, 1 warning (0.00 sec) mysql> select '2017-10-25' - 17; +-------------------+ | '2017-10-25' - 17 | +-------------------+ | 2000 | +-------------------+ 1 row in set, 1 warning (0.00 sec) mysql> select '2017-10-17' * 2; +-------------------+ | '2017-10-17' * 20 | +-------------------+ | 4034 | +-------------------+ 1 row in set, 1 warning (0.00 sec) mysql> select '2017-05-25'/5; +----------------+ | '2017-05-25'/5 | +----------------+ | 403.4 | +----------------+ 1 row in set, 1 warning (0.00 sec)
