MySQL系统信息函数有：
VERSION() 返回数据库的版本号
CONNECTION_ID() 返回服务器的连接数
DATABASE() ,
SCHEMA() 返回当前数据库名
USER() ,
SYSTEM_USER() 返回当前用户
CURRENT_USER() ,
CURRENT_USER 返回当前用户
CHARSET(STR) 返回字符串STR的字符集
LAST_INSERT_ID() 返回最近生成的AUTO_INCREMENT值
mysql> SELECT VERSION();
+-----------+
| VERSION() |
+-----------+
| 5.6.23 |
+-----------+
1 row in set (0.00 sec)
mysql> SELECT CONNECTION_ID();
+-----------------+
| CONNECTION_ID() |
+-----------------+
| 3 |
+-----------------+
1 row in set (0.00 sec)
mysql> SELECT DATABASE();
+------------+
| DATABASE() |
+------------+
| learndb1 |
+------------+
1 row in set (0.00 sec)
mysql> SELECT USER();
+----------------+
| USER() |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.01 sec)
mysql> SELECT CURRENT_USER();
+----------------+
| CURRENT_USER() |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.00 sec)
mysql> SELECT CHARSET('字符');
+-------------------+
| CHARSET('字符') |
+-------------------+
| utf8 |
+-------------------+
1 row in set (0.00 sec)