常用sql语句与mysql备份恢复

mysql> select count(*) from t1;  //查询某个表的行数
+----------+
| count(*) |
+----------+
|        0 |
+----------+
1 row in set (0.00 sec)

mysql> select count(*) from mysql.user;
+----------+
| count(*) |
+----------+
|       15 |
+----------+
1 row in set (0.01 sec)

mysql> select * from mysql.user\G   //查看某个表的所有数据
*********** 1. row ***********
Host: localhost
User: root
Password: *5CE29D9A76C0BB86C8B4CE8B06D050D817316437
Select_priv: Y
Insert_priv: Y

mysql> select host,user,password from mysql.user;  //查看指定的字段
+----------------+---------+-------------------------------------------+
| host           | user    | password                                  |
+----------------+---------+-------------------------------------------+
| localhost      | root    | *5CE29D9A76C0BB86C8B4CE8B06D050D817316437 |
| cent01         | root    | *5CE29D9A76C0BB86C8B4CE8B06D050D817316437 |
| 127.0.0.1      | root    | *5CE29D9A76C0BB86C8B4CE8B06D050D817316437 |
| ::1            | root    | *5CE29D9A76C0BB86C8B4CE8B06D050D817316437 |
| localhost      |         |                                           |
| cent01         |         |                                           |
| 127.0.0.1      | user1   | *B012E8731FF1DF44F3D8B26837708985278C3CED |
| localhost      | user2   | *B012E8731FF1DF44F3D8B26837708985278C3CED |
| localhost      | user1   | *B012E8731FF1DF44F3D8B26837708985278C3CED |

mysql> select * from mysql.user where host like '192.168%'\G  //使用%进行模糊查询
**************** 1. row **************
Host: 192.168.133.1
User: user2
Password: *59C70DA2F3E3A5BDF46B68F5C8B8F25762BCCEF0
Select_priv: N
Insert_priv: N
Update_priv: N

mysql> desc t1;  //先查看需要更改的表有多少个字段以及字段类型
+-------+----------+------+-----+---------+-------+
| Field | Type     | Null | Key | Default | Extra |
+-------+----------+------+-----+---------+-------+
| id    | int(4)   | YES  |     | NULL    |       |
| name  | char(40) | YES  |     | NULL    |       |
+-------+----------+------+-----+---------+-------+
2 rows in set (0.01 sec)

mysql> insert db3.t1 values(1,'abc'); //按对应的字段输入值
Query OK, 1 row affected (0.01 sec)

mysql> select * from db3.t1;  //查看输入后表的变化
+------+------+
| id   | name |
+------+------+
|    1 | abc  |
+------+------+
1 row in set (0.00 sec)

mysql> insert db3.t1 values (1,2,'c');   //如果字段数不符，报错
ERROR 1136 (21S01): Column count doesn't match value count at row 1

mysql> insert db3.t1 values (2,c);  //字段类型不符，报错
ERROR 1054 (42S22): Unknown column 'c' in 'field list'

mysql> select * from db3.t1; //查看原值
+------+------+
| id   | name |
+------+------+
|    1 | abc  |
|    1 | 2    |
|    2 | c    |
+------+------+
3 rows in set (0.00 sec)

mysql> update db3.t1 set name='wewewe' where id='1';  //更改值
Query OK, 2 rows affected (0.01 sec)
Rows matched: 2  Changed: 2  Warnings: 0

mysql> select * from db3.t1; //更改后的值
+------+--------+
| id   | name   |
+------+--------+
|    1 | wewewe |
|    1 | wewewe |
|    2 | c      |
+------+--------+
3 rows in set (0.00 sec)

truncate table db3.t1 //清空表的数据，但结构和字段还在

drop table db3.t1 //直接删除表

drop database db3 //直接删除数据库

数据库备份与恢复

[root@cent01 tmp]# mysqldump -uroot -paming db2>/tmp/db2.sql  //备份用mysqldump
Warning: Using a password on the command line interface can be insecure.

[root@cent01 tmp]# mysql -uroot -paming db2</tmp/mysql.sql //恢复直接用mysql
Warning: Using a password on the command line interface can be insecure.

mysql> show tables;  //对比发现恢复时，不会覆盖备份文件中没有的字段。例如t1表。
+---------------------------+
| Tables_in_db2             |
+---------------------------+
| columns_priv              |
| db                        |
| event                     |
| func                      |
| t1                        |

备份表 mysqldump -uroot -p123456 mysql user > /tmp/user.sql
恢复表 mysql -uroot -p123456 mysql < /tmp/user.sql
备份所有库 mysqldump -uroot -p -A >/tmp/123.sql
只备份表结构 mysqldump -uroot -p123456 -d mysql > /tmp/mysql.sql