mysql> alter table 国产 rename to guochan;

习惯上函数用大写，但小写也可以

mysql> select now();

select ascii('f');

返回字符串str的第一个字符的ASCII值(str是空串时返回0),总是加单引号。

select CHAR(77,121,83,86,77);

增删改查语句

MariaDB [EMP]> insert into Employees values (100,18,'aa','bb');

Query OK, 1 row affected (0.02 sec)

MariaDB [EMP]> insert into Employees values (101,19,'a2','b2');

Query OK, 1 row affected (0.02 sec)

MariaDB [EMP]> insert into Employees values (101,19,'zara','b3');

Query OK, 1 row affected (0.01 sec)

MariaDB [EMP]> insert into Employees values (105,30,'a4','b4');

Query OK, 1 row affected (0.01 sec)

MariaDB [EMP]> select * from Employees;

+-----+-----+-------+------+

| id  | age | first | last |

+-----+-----+-------+------+

| 100 |  18 | aa    | bb   |

| 101 |  19 | a2    | b2   |

| 101 |  19 | zara  | b3   |

| 105 |  30 | a4    | b4   |

+-----+-----+-------+------+

4 rows in set (0.00 sec)

MariaDB [EMP]> UPDATE Employees SET id=102 WHERE first='zara';

Query OK, 1 row affected (0.01 sec)

Rows matched: 1  Changed: 1  Warnings: 0

MariaDB [EMP]> select * from Employees;

+-----+-----+-------+------+

| id  | age | first | last |

+-----+-----+-------+------+

| 100 |  18 | aa    | bb   |

| 101 |  19 | a2    | b2   |

| 102 |  19 | zara  | b3   |

| 105 |  30 | a4    | b4   |

+-----+-----+-------+------+

4 rows in set (0.00 sec)

MariaDB [EMP]> delete from Employees where id=105;

MariaDB [EMP]> select * from Employees;

+-----+-----+-------+------+

| id  | age | first | last |

+-----+-----+-------+------+

| 100 |  18 | aa    | bb   |

| 101 |  19 | a2    | b2   |

| 102 |  19 | zara  | b3   |

+-----+-----+-------+------+

3 rows in set (0.00 sec)

MariaDB [EMP]> insert into Employees values(108,29,'wu','ma');

Query OK, 1 row affected (0.03 sec)

MariaDB [EMP]> insert into Employees values(109,26,'wang','wei');

Query OK, 1 row affected (0.02 sec)

MariaDB [EMP]> select * from Employees;

+-----+-----+-------+------+

| id  | age | first | last |

+-----+-----+-------+------+

| 100 |  18 | aa    | bb   |

| 101 |  19 | a2    | b2   |

| 102 |  19 | zara  | b3   |

| 108 |  29 | wu    | ma   |

| 109 |  26 | wang  | wei  |

+-----+-----+-------+------+

5 rows in set (0.00 sec)

show variables like '%FOREIGN%';
SET FOREIGN_KEY_CHECKS=0;

delete from geographical_position where type = 1
select distinct type from geographical_position

mysql> create user 'ab'@'localhost' identified by 'weeee';
mysql> select user,host,password from mysql.user;

INSERT(str,pos,len,newstr)
instr

mysql> select instr('contents','t');
+-----------------------+
| instr('contents','t') |
+-----------------------+
|                     4 |
+-----------------------+
1 row in set (0.00 sec)

mysqldump -u root -d -R --add-drop-table spa >spa.sql
sed -i '1i\use spa;' spa.sql
sed -i '1i\create database spa;' spa.sql
sed -i '1i\drop database if exists spa;' spa.sql
mysqldump -u root   --add-drop-table spa action_buttons>>spa.sql
mysqldump -u root   --add-drop-table spa menu>>spa.sql
mysqldump -u root   --add-drop-table --extended-insert=false spa tb_sequence>>spa.sql
mysqldump -u root   --add-drop-table spa role --where="id=20" >>spa.sql
mysqldump -u root   --add-drop-table spa role_button_relation --where="role_id=20" >>spa.sql
mysqldump -u root   --add-drop-table spa user_role_relation --where="role_id=20" >>spa.sql
mysqldump -u root   --add-drop-table spa system_user --where="username='admin'" >>spa.sql

-d, --no-data       No row information.
-R, --routines      Dump stored routines (functions and procedures).

select * from tb_sequence limit 0,1
limit是mysql的语法
select * from table limit m,n
其中m是指记录开始的index，从0开始，表示第一条记录
n是指从第m+1条开始，取n条。
select * from tablename limit 2,4
即取出第3条至第6条，4条记录

[root@db mysql]# mysqlshow
[root@db mysql]# mysql -e 'select user,password,host from mysql.user'
mysql> delete from user where user = '';    删除匿名用户
mysql> drop user ''@localhost ;