它对您来说只是空白，因为您尚未设置sql_mode。如果您进行设置，则该查询将向您显示详细信息：
mysql> SELECT @@sql_mode;+------------+| @@sql_mode |+------------+| |+------------+1 row in set (0.00 sec)mysql> set sql_mode=ORACLE;Query OK, 0 rows affected (0.00 sec)mysql> SELECT @@sql_mode;+----------------------------------------------------------------------------------------------------------------------+| @@sql_mode |+----------------------------------------------------------------------------------------------------------------------+| PIPES_AS_CONCAT,ANSI_QUOTES,IGNORE_SPACE,ORACLE,NO_KEY_OPTIONS,NO_TABLE_OPTIONS,NO_FIELD_OPTIONS,NO_AUTO_CREATE_USER |+----------------------------------------------------------------------------------------------------------------------+1 row in set (0.00 sec)
