标签：mysql
1、mysql使用
1）客户端命令：命令在客户端执行，不需要命令终止符，通常默认为分号“;”
\q|quit|exit
\?|?|h|help
\g:把命令发送给服务器端执行，相当于“；”
\G：把行分段显示
\c：取消命令执行
mysql> SELECT user,host,password from mysql.user\g +------+------------+-------------------------------------------+ | user | host | password | +------+------------+-------------------------------------------+ | root | localhost | *CC67043C7BCFF5EEA5566BD9B1F3C74FD9A5CF5D | | root | BAIYU\_179 | | | root | 127.0.0.1 | *CC67043C7BCFF5EEA5566BD9B1F3C74FD9A5CF5D | | | BAIYU\_179 | | +------+------------+-------------------------------------------+ 4 rows in set (0.00 sec) mysql> SELECT user,host,password from mysql.user\G *************************** 1. row *************************** user: root host: localhost password: *CC67043C7BCFF5EEA5566BD9B1F3C74FD9A5CF5D *************************** 2. row *************************** user: root host: BAIYU\_179 password: *************************** 3. row *************************** user: root host: 127.0.0.1 password: *CC67043C7BCFF5EEA5566BD9B1F3C74FD9A5CF5D *************************** 4. row *************************** user: host: BAIYU\_179 password: 4 rows in set (0.00 sec)
2）服务器端命令：命令发送到服务器端执行
BIF:内建函数
SELECT,
选取选部分行)和投影（选部分列）
select col1,col2,...from tb1,tb2,...where clause;
where col1 > 30;
SHOW DATABASES; 显示有权限查看的所有库
USE database_name:使用某库
SHOW TABLES; 显示其库所有表
CREATE DATABASE database_name;创建库
DROP DATABASE database_name;删除某库
mysql> SELECT CURRENT_TIME(); +----------------+ | CURRENT_TIME() | +----------------+ | 00:10:18 | +----------------+ 1 row in set (0.00 sec)
命令帮助的获取：mysql> help KEYWORD
命令不区分字符大小写（建议大写），但与文件系统相关的部分是否区分大小写根据OS
3）mysql使用:
交互模式：
非交互|批处理模式：
[root@BAIYU_179 ~]# mysql -uroot -p123456789 -e ‘SELECT USER();‘ +----------------+ | USER() | +----------------+ | root@localhost | +----------------+ [root@BAIYU_179 ~]# echo -e "SHOW DATABASES;\nCREATE DATABASE testdb;\nSHOW DAT ABASES;" > a.sql [root@BAIYU_179 ~]# mysql -uroot -p123456789 < a.sql Database information_schema mysql performance_schema test Database information_schema mysql performance_schema test testdb
4）键：key
约束：constraint
主键约束：对一张表来讲，主键只能有一个，主键数据不能相同，主键不能为空（NULL）
唯一键约束：可以为NULL，可以有多个
外键约束：
检查式约束：用户自定义有效取值范围
键：就是选取出来的字段
主键：能唯一标识表中每一个记录的字段或字段的组合
候选键：能作为主键的字段，
5）表：table
由行和列组成的而为关系
字段：字段名，约束，字段类型
创建表：
CREATE TABLE table_name(col1_name col1_type 修饰符,col2 col2_type 修饰符...);
删除表：
DROP TABLE table_name;
字段或字段类型还可以有修饰符：
NOT NULL:不能为空
NULL：可为空
UNSIGNED:无符号，无负值
DEFAULT：
AUTO_INCREMENT:自动增长类型的字段必须为主键或唯一键
PRIMARY KEY:主键，如何把多个字段定义为主键则用括号把多个字段括起来在后面加PRIMARY KEY
字符要加上引号，数值不能加引号
mysql> CREATE TABLE students(name varchar(30),age tinyint,gender ENUM(‘f‘,‘m‘)) ; Query OK, 0 rows affected (0.02 sec) mysql> DESCRIBE students; +--------+---------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------+---------------+------+-----+---------+-------+ | name | varchar(30) | YES | | NULL | | | age | tinyint(4) | YES | | NULL | | | gender | enum(‘f‘,‘m‘) | YES | | NULL | | +--------+---------------+------+-----+---------+-------+ 3 rows in set (0.00 sec) mysql> DROP TABLE students; Query OK, 0 rows affected (0.01 sec) mysql> SHOW TABLES; Empty set (0.00 sec) mysql> CREATE TABLE students(name varchar(30) NOT NULL,age tinyint UNSIGNED NOT NULL,gender ENUM(‘F‘,‘M‘) DEFAULT ‘M‘); Query OK, 0 rows affected (0.00 sec) mysql> DESC students; +--------+---------------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------+---------------------+------+-----+---------+-------+ | name | varchar(30) | NO | | NULL | | | age | tinyint(3) unsigned | NO | | NULL | | | gender | enum(‘F‘,‘M‘) | YES | | M | | +--------+---------------------+------+-----+---------+-------+ 3 rows in set (0.00 sec) mysql> CREATE TABLE students(stuID int UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY, name varchar(30) NOT NULL,age tinyint UNSIGNED NOT NULL,gender ENUM(‘F‘,‘ M‘) NOT NULL DEFAULT ‘M‘); Query OK, 0 rows affected (0.01 sec) mysql> DESC students; +--------+---------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +--------+---------------------+------+-----+---------+----------------+ | stuID | int(10) unsigned | NO | PRI | NULL | auto_increment | | name | varchar(30) | NO | | NULL | | | age | tinyint(3) unsigned | NO | | NULL | | | gender | enum(‘F‘,‘M‘) | NO | | M | | +--------+---------------------+------+-----+---------+----------------+ 4 rows in set (0.00 sec)
6）数据
插入：
INSERT INTO table_name(col1,col2,...) value|values(val1,val2,...)
INSERT INTO table_name VALUES(val1,val2,...)
mysql> INSERT INTO students values(1,‘xj‘,25,‘M‘); Query OK, 1 row affected (0.01 sec) mysql> SELECT * FROM students; +-------+------+-----+--------+ | stuID | name | age | gender | +-------+------+-----+--------+ | 1 | xj | 25 | M | +-------+------+-----+--------+ 1 row in set (0.00 sec) mysql> INSERT INTO students values(2,‘xxj‘,23,‘M‘),(3,‘xiexiaojun‘,24,‘M‘); Query OK, 2 rows affected (0.01 sec) Records: 2 Duplicates: 0 Warnings: 0 mysql> SELECT * FROM students; +-------+------------+-----+--------+ | stuID | name | age | gender | +-------+------------+-----+--------+ | 1 | xj | 25 | M | | 2 | xxj | 23 | M | | 3 | xiexiaojun | 24 | M | +-------+------------+-----+--------+ 3 rows in set (0.00 sec) mysql> INSERT INTO students(name,gender) value(‘xx‘,‘M‘),(‘xiexie‘,‘F‘); Query OK, 2 rows affected, 1 warning (0.00 sec) Records: 2 Duplicates: 0 Warnings: 1 mysql> SELECT * FROM students; +-------+------------+-----+--------+ | stuID | name | age | gender | +-------+------------+-----+--------+ | 1 | xj | 25 | M | | 2 | xxj | 23 | M | | 3 | xiexiaojun | 24 | M | | 4 | xx | 0 | M | | 5 | xiexie | 0 | F | +-------+------------+-----+--------+ 5 rows in set (0.00 sec)
查询：
SELECT col1,col2,... FROM table_name WHERE; 条件表达式；
SELECT * FROM table_name;
mysql> SELECT name,age,gender FROM students WHERE age>20; +------------+-----+--------+ | name | age | gender | +------------+-----+--------+ | xj | 25 | M | | xxj | 23 | M | | xiexiaojun | 24 | M | +------------+-----+--------+ 3 rows in set (0.00 sec) mysql> SELECT name,age,gender FROM students WHERE gender=F; ERROR 1054 (42S22): Unknown column ‘F‘ in ‘where clause‘ mysql> SELECT name,age,gender FROM students WHERE gender=‘F‘; +--------+-----+--------+ | name | age | gender | +--------+-----+--------+ | xiexie | 0 | F | +--------+-----+--------+ 1 row in set (0.00 sec) mysql> SELECT name,age,gender FROM students WHERE age<25 AND gender=‘F‘; +--------+-----+--------+ | name | age | gender | +--------+-----+--------+ | xiexie | 0 | F | +--------+-----+--------+ 1 row in set (0.00 sec)
删除：
DELETE FROM table_name;
DELETE FORM table_name WHERE 条件表达式;
LIKE:匹配通配符
%：任意长度的任意字符
_:任意单个字符
RLIKE:正则表达式
mysql> DELETE FROM students WHERE age<20; Query OK, 2 rows affected (0.00 sec) mysql> SELECT * FROM students; +-------+------------+-----+--------+ | stuID | name | age | gender | +-------+------------+-----+--------+ | 1 | xj | 25 | M | | 2 | xxj | 23 | M | | 3 | xiexiaojun | 24 | M | +-------+------------+-----+--------+ 3 rows in set (0.00 sec) mysql> DELETE FROM students WHERE NAME LIKE ‘%o%‘; Query OK, 1 row affected (0.02 sec) mysql> SELECT * FROM students; +-------+------+-----+--------+ | stuID | name | age | gender | +-------+------+-----+--------+ | 1 | xj | 25 | M | | 2 | xxj | 23 | M | +-------+------+-----+--------+ 2 rows in set (0.00 sec)
更新：
UPDATE table_name SET col1=values,col2=values,...；
UPDATE table_name SET col1=values,... WHERE 条件表达式；
mysql> UPDATE students SET age=30; Query OK, 2 rows affected (0.02 sec) Rows matched: 2 Changed: 2 Warnings: 0 mysql> SELECT * FROM students; +-------+------+-----+--------+ | stuID | name | age | gender | +-------+------+-----+--------+ | 1 | xj | 30 | M | | 2 | xxj | 30 | M | +-------+------+-----+--------+ 2 rows in set (0.00 sec) mysql> UPDATE students SET age=33 WHERE STUID=1; Query OK, 1 row affected (0.01 sec) Rows matched: 1 Changed: 1 Warnings: 0 mysql> SELECT * FROM students; +-------+------+-----+--------+ | stuID | name | age | gender | +-------+------+-----+--------+ | 1 | xj | 33 | M | | 2 | xxj | 30 | M | +-------+------+-----+--------+ 2 rows in set (0.00 sec)
2、字段|数据类型
字符型：
char(N)：固定长度，N指字符数，不区分大小写
varchar(N)：可变长度,N指最大字符数，不区分大小写
binary（N）：区分大小写
varbinary(N):区分大小写
text（N）:大段文本，不区分大小写
blob（N）:大段文本，区分大小写
数值型：
精确数值型：
int(整形)：tinyint(微，1B)，smallint(小，2B)，mediumint(中，3B)，int(4B),bigint(大，4B)
decimal（十进制）
近似数值型：
float:单精度
double:双精度
日期时间型：
date,3B
time,3B
datetime,8B
timestamp:时间戳
布尔型：
NULL:
内置类型：
ENUM:枚举型（一定范围内跳一个，字符型）
SET:集合型（集合内字符任意组合，不能使用集合外的字符）
数据类型的作用：
比较方式：排序方式
存储空间：取值范围
参与的运算：
标签：mysql
原文地址：http://xiexiaojun.blog.51cto.com/2305291/1710127
