查询某个数据库中表个数的sql语句
SELECT COUNT(*) TABLES, table_schema FROM information_schema.TABLES WHERE table_schema = 'db_name' GROUP BY table_schema;
查看自己的mysql数据库支持的引擎有哪些
mysql> show engines;
Mysql提供函数datediff来输出两个日期之间相差的天数
mysql> SELECT DATEDIFF('2017-04-08','2017-04-01') AS DiffDate;
+----------+
| DiffDate |
+----------+
| 7 |
+----------+
1 row in set (0.00 sec)