一 查看当前MySQL版本号
mysql> SELECT VERSION();
+-----------+
| VERSION() |
+-----------+
| 5.7.22 |
+-----------+
1 row in set (0.00 sec)
二 查看当前用户的连接数
mysql> SELECT CONNECTION_ID();
+-----------------+
| CONNECTION_ID() |
+-----------------+
| 2 |
+-----------------+
1 row in set (0.00 sec)
三 使用SHOW PROCESSLIST命令输出当前用户的连接信息
mysql> SHOW PROCESSLIST;
+----+------+------+------+---------+------+----------+------------------+
| Id | User | Host | db | Command | Time | State | Info |
+----+------+------+------+---------+------+----------+------------------+
| 2 | root | | test | Query | 0 | starting | SHOW PROCESSLIST |
+----+------+------+------+---------+------+----------+------------------+
1 row in set (0.00 sec)
四 查看当前使用的数据库
mysql> SELECT DATABASE(),SCHEMA();
+------------+----------+
| DATABASE() | SCHEMA() |
+------------+----------+
| test | test |
+------------+----------+
1 row in set (0.00 sec)
五 获取当前登录用户名称
mysql> SELECT USER(), CURRENT_USER(), SYSTEM_USER();
+--------+-----------------------------------+---------------+
| USER() | CURRENT_USER() | SYSTEM_USER() |
+--------+-----------------------------------+---------------+
| root@ | skip-grants user@skip-grants host | root@ |
+--------+-----------------------------------+---------------+
1 row in set (0.00 sec)
六 使用CHARSET()函数返回字符串使用的字符集
SELECT CHARSET('abc'),
CHARSET(CONVERT('abc' USING latin1)),
CHARSET(VERSION());
+----------------+--------------------------------------+--------------------+
| CHARSET('abc') | CHARSET(CONVERT('abc' USING latin1)) | CHARSET(VERSION()) |
+----------------+--------------------------------------+--------------------+
| utf8 | latin1 | utf8 |
+----------------+--------------------------------------+--------------------+
1 row in set (0.00 sec)
七 使用COLLATION()函数返回字符串排列方式
mysql> SELECT COLLATION('abc'),COLLATION(CONVERT('abc' USING utf8));
+------------------+--------------------------------------+
| COLLATION('abc') | COLLATION(CONVERT('abc' USING utf8)) |
+------------------+--------------------------------------+
| utf8_general_ci | utf8_general_ci |
+------------------+--------------------------------------+
1 row in set (0.00 sec)
参考: https://www.cnblogs.com/EasonJim/p/8128196.html
八 使用SELECT LAST_INSERT_ID查看最后一个自动生成的列值
1.一次插入一条记录
首先创建表worker,其Id字段带有AUTO_INCREMENT约束
CREATE TABLE worker (Id INT AUTO_INCREMENT NOT NULL PRIMARY KEY,
Name VARCHAR(30));
Query OK, 0 rows affected (0.23 sec)
分别单独向表worker中插入2条记录:
mysql> INSERT INTO worker VALUES(NULL, 'jimy');
Query OK, 1 row affected (0.03 sec)
mysql> INSERT INTO worker VALUES(NULL, 'Tom');
Query OK, 1 row affected (0.02 sec)
mysql> SELECT * FROM worker;
+----+------+
| Id | Name |
+----+------+
| 1 | jimy |
| 2 | Tom |
+----+------+
2 rows in set (0.00 sec)
查看已经插入的数据可以发现,最后一条插入的记录的Id字段值为2,使用LAST_INSERT_ID()查看最后自动生成的Id值:
mysql> SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
| 2 |
+------------------+
1 row in set (0.01 sec)
2.一次同时插入多条记录
接下来,向表中插入多条记录
INSERT INTO worker VALUES
(NULL, 'Kevin'),(NULL,'Michal'),(NULL,'Nick');
Query OK, 3 rows affected (0.03 sec)
Records: 3 Duplicates: 0 Warnings: 0
查询已经插入的的记录,
mysql> SELECT * FROM worker;
+----+--------+
| Id | Name |
+----+--------+
| 1 | jimy |
| 2 | Tom |
| 3 | Kevin |
| 4 | Michal |
| 5 | Nick |
+----+--------+
5 rows in set (0.00 sec)
mysql> SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
| 3 |
+------------------+
1 row in set (0.00 sec)