mysql> alter table 国产 rename to guochan;<br/>
习惯上函数用大写，但小写也可以<br/>
mysql> select now();<br/>
select ascii('f');<br/>
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。<br/>
select CHAR(77,121,83,86,77);

增删改查语句

MariaDB [EMP]> insert into Employees values (100,18,'aa','bb');<br/>
Query OK, 1 row affected (0.02 sec)

MariaDB [EMP]> insert into Employees values (101,19,'a2','b2');<br/>
Query OK, 1 row affected (0.02 sec)

MariaDB [EMP]> insert into Employees values (101,19,'zara','b3');<br/>
Query OK, 1 row affected (0.01 sec)

MariaDB [EMP]> insert into Employees values (105,30,'a4','b4');<br/>
Query OK, 1 row affected (0.01 sec)

MariaDB [EMP]> select * from Employees;<br/>
+-----+-----+-------+------+<br/>
| id  | age | first | last |<br/>
+-----+-----+-------+------+<br/>
| 100 |  18 | aa    | bb   |<br/>
| 101 |  19 | a2    | b2   |<br/>
| 101 |  19 | zara  | b3   |<br/>
| 105 |  30 | a4    | b4   |<br/>
+-----+-----+-------+------+<br/>
4 rows in set (0.00 sec)

MariaDB [EMP]> UPDATE Employees SET id=102 WHERE first='zara';<br/>
Query OK, 1 row affected (0.01 sec)<br/>
Rows matched: 1  Changed: 1  Warnings: 0

MariaDB [EMP]> select * from Employees;<br/>
+-----+-----+-------+------+<br/>
| id  | age | first | last |<br/>
+-----+-----+-------+------+<br/>
| 100 |  18 | aa    | bb   |<br/>
| 101 |  19 | a2    | b2   |<br/>
| 102 |  19 | zara  | b3   |<br/>
| 105 |  30 | a4    | b4   |<br/>
+-----+-----+-------+------+<br/>
4 rows in set (0.00 sec)

MariaDB [EMP]> delete from Employees where id=105;<br/>
MariaDB [EMP]> select * from Employees;<br/>
+-----+-----+-------+------+<br/>
| id  | age | first | last |<br/>
+-----+-----+-------+------+<br/>
| 100 |  18 | aa    | bb   |<br/>
| 101 |  19 | a2    | b2   |<br/>
| 102 |  19 | zara  | b3   |<br/>
+-----+-----+-------+------+<br/>
3 rows in set (0.00 sec)

MariaDB [EMP]> insert into Employees values(108,29,'wu','ma');<br/>
Query OK, 1 row affected (0.03 sec)

MariaDB [EMP]> insert into Employees values(109,26,'wang','wei');<br/>
Query OK, 1 row affected (0.02 sec)

MariaDB [EMP]> select * from Employees;<br/>
+-----+-----+-------+------+<br/>
| id  | age | first | last |<br/>
+-----+-----+-------+------+<br/>
| 100 |  18 | aa    | bb   |<br/>
| 101 |  19 | a2    | b2   |<br/>
| 102 |  19 | zara  | b3   |<br/>
| 108 |  29 | wu    | ma   |<br/>
| 109 |  26 | wang  | wei  |<br/>
+-----+-----+-------+------+<br/>
5 rows in set (0.00 sec)

show variables like '%FOREIGN%';<br/>SET FOREIGN_KEY_CHECKS=0;

delete from geographical_position where type = 1<br/>select distinct type from geographical_position

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

INSERT(str,pos,len,newstr)<br/>instr

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

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

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

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

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