mysql的常用数据类型和数据类型修饰

后面的带数字表示此类型的字段长度

数值型：

TINYINT 1 ，SMALLINT 2，MEDIUMINT 3 ，INT 4，BIGINT 8，DECIMAL，FLOAT 4，DOUBLE 8，BIT

字符串型

CHAR，VARCHAR，BINARY，VBINARY,TINYBLOB，BLOB，MEDIUMBLOB，LONGBLOG，TINYTEXT，TEXT，MEDIUMTEXT，LONGTEXT，EMUM，SET

日期时间型

date,time,datetime,timestamp

数据限定修饰：

NOT NULL，NULL，DEFAULT，AUTO_INCREMENT，UNSIGNED，PRIMARY KEY，UNIQUE KEY，FOREIGN KEY

CHARACTER SET #ps:SHOW CHARACTER SET 显示当前数据库所支持的所有字符集

COLLATION #ps:SHOW COLLATION 显示所支持的所有排序规则

以下是SQL的每种DDL,DCL,DML语言

DDL

----Data Definition Language 数据库定义语言

如 create procedure之类

创建数据库

CREATE DATABASE [IF NOT EXISTS] DBNAME [CHARACTER SET 'CHAR_NAME'] [COLLATE 'COLL_NAME']

修改:ALTER 删除:DROP

创建一张新表

CRTATE TABLE [IF NOT EXISTS] TBNAME(col_name col_definition,...)

EXAMPLE:

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mysql>CREATE TABLE students(Id INT PRIMARY KEY NOT NULL AUTO_INCREMENT UNSIGNED,Name CHAR(20) UNIQUE KEY NOT NULL,Age TINYINT UNSIGNED INDEX,Gender CHAR(1) NOT NULL) [ENGINE={MyISAM | InnoDB }];

也可以这样写(区别在于单独定义主键，唯一键和索引)：

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mysql>CREATE TABLE students(Id INT NOT NULL AUTO_INCREMENT UNSIGNED,Name CHAR(20) NOT NULL,Age TINYINT UNSIGNED,Gender CHAR(1) NOT NULL,PRIMARY KEY(id),UNIQUE KEY(name),INDEX(age))

查询出一张表的数据后创建新表(字段定义会丢失,数据会保留)

CREATE TABLE TBNAME SELECT...

EXAMPLE:

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mysql>CREATE TABLE test SELECT * FROM students WHERE Id>5;

以一张表的格式定义，创建一张新的空表

CREATE TABLE TBNAME1 LIKE TBNAME2

修改表:

ALTER TABLE tb_name

MODIFY #修改字段定义

CHANGE #可以修改字段名和字段定义

ADD

DROP

EXAMPLE:

给表添加字段

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mysql>ALTER TABLE students ADD (course VARCHAR(100),teacher CHAR(20));

添加惟一键

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mysql>ALTER TABLE students ADD UNIQUE KEY Name;

修改字段：

修改course字段为Course字段，并放在Name字段之后(修改字段需要带上新的字段的定义)ps：MODIFY只能修改字段定义

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mysql>ALTER TABLE students CHANGE course Course VARCHAR(100) [AFTER Name];

重命名表名

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mysql>ALTER TABLE students RENAME TO stu;

mysql>RENAME TABLE stu TO students;

添加一个外键约束

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ALTER TABLE students ADD FOREIGN KEY foreign _cid (CID) REFERENCES course (CID);

创建索引

CREATE INDEX index_name ON TABLE (col_name[(length)] [ASC|DESC]) [USING {BTREE|HASH}];

删除索引

DROP INDEX index_name ON TBNAME;

查看表状态:SHOW STATUS LIKE 'TBNAME';

查看表的索引:SHOW INDEXES FROM TBNAME;

DML

----Data Manipulation Language 数据操纵语言

如insert,delete,update,select(插入、删除、修改、检索)

插入修改数据

#如果每个字段都有值，不需要写字段名称,每组值用,隔开

mysql>INSERT INTO tb_name (col1,col2) VALUES ('STRING',NUM),('STRING',NUM);

mysql>INSERT INTO tb_name SET col1='string',col2='string';

mysql>INSERT INTO tb_name (col1,col2,col3) SELECT...;

EXAMPLE:

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mysql>INSERT INTO students (Name,Gender,teacher) VALUE ('lujunyi','M','mage'),('wusong','M','zhuima');

mysql>INSERT INTO students SET Name='lujunyi',Gender='M',tearcher='zhuima';

更新数据

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mysql>UPDATE tb_name SET column=value WHERE column=value;

mysql>UPDATE students SET Course='mysql' WHERE Name='lujunyi';

替换数据：

和UPDATE使用方式一样,只要将UPDATE换成REPLACE即可

删除数据

mysql>DELETE FROM tb_name WHERE conditions;

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mysql>DELETE FROM students WHERE Course='mysql';

清空表：将会重置计数器

mysql>TRUNCATE tb_name

查询数据

单表查询：

mysql>SELECT [DISTINCT] column FROM tb_name WHERE CONDITION;

EXAMPLE:

#基本投影查询

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mysql>SELECT Name,teacher FROM students WHERE Name='wusong';

#重复的结果只显示一次

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mysql>SELECT DISTINCT Gender FROM students;

#组合条件,可以使用AND,OR,NOT,XOR组合多个条件

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mysql>SELECT * FROM students WHERE Age>20 AND Gender='M';

#使用BETWEEN...AND...筛选出年龄介于20-25之间的数据

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mysql>SELECT * FROM students WHERE Age BETWEEN 20 AND 25;

#查询Name以Y开头的的数据，%表示任意长度的任意字符，_表示任意单个字符

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mysql>SELECT * FROM student WHERE Name LIKE 'Y%';

#使用正则表达式匹配查询,关键词为RLINK或者REGEXP

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mysql> SELECT * FROM students WHERE Name RLINK '^[MNY].*$';

#使用IN关键词，将条件限定在一个列表中。用IS关键词，表示条件是否为空(IS NULL 或者 IS NOT NULL)

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mysql>SELECT * FROM students WHERE Age IN (20,22,24);

#将查询的结果进行排序

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mysql>SELECT * FROM students ORDER BY Name {ASC|DESC};

#查询结果别名显示

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mysql>SELECT Name AS Stu_Name FROM students;

#LIMIT限定查询结果的条数,LIMIT 2,3表示偏移2条数据后，取3条数据

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mysql>SELECT * FROM students LIMIT 2;

#求平均数:AVG()，最大值:MAX() 最小值MIN() 数量:COUNT() 求和:SUM()

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mysql>SELECT AVG(age) FROM students;

#分组GROUP BY

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mysql>SELECT Age, Gender FROM students GROUP BY Gender;

#别名:AS

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mysql>SELECT COUNT(Age) AS Num,Age FROM students GROUP BY Age;

#过滤:HAVING

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mysql>SELECT COUNT(Age) AS Num,Age FROM students GROUP BY Age HAVING Num>2;

多表查询:

#指定已哪个字段连接2张表

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mysql>SELECT students.Name,courses.Cname FROM students,courses WHERE students.CID1 = courses.CID;

#连接时指定别名

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mysql>SELECT students.Name,courses.Cname FROM students,courses WHERE students.CID1 = courses.CID;

#左外连接...LEFT JION...ON...

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mysql>SELECT s.Name,c.Cname FROM students AS s LEFT JION courses AS c ON s.CID1=c.CID;

#右外连接...RIGHT JION...ON...

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mysql>SELECT s.Name,c.Cname FROM students AS s RIGHT JION courses AS c ON s.CID1=c.CID;

子查询

#查询年龄大于平均年龄的数据

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mysql>SELECT * FROM students WHERE Age > (SELECT AVG(Age) FROM students);

#在FROM中使用子查询

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mysql>SELECT Name,Age FROM (SELECT * FROM students WHERE CID IN (2,3)) AS t WHERE Age>20;

#联合查询

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mysql>(SELECT Name,Age FROM students) UNION (SELECT Tname,Age FROM tutors);

创建视图

CREATE VIEW VIEW_NAME AS SELECT....

DCL

----Data Control Language 数据库控制语言

如grant,deny,revoke等，只有管理员才有这样的权限。

创建用户

mysql>CREATE USER 'USERNAME'@'HOST' IDENTIFIED BY 'PASSWORD'

删除用户

mysql>DROP USER 'USERNAME'@'HOSHOST支持通配符

_:任意单个字符

%:任意多个字符

授权

mysql>GRANT pri1,pri2...ON DB_NAME.TB_NAME TO 'USERNAME'@'HOST' [IDENTIFIED BY 'PASSWORD']

取消授权

mysql>REVOKE pri1,pri2...ON DB_NAME.TB_NAME FROM 'USERNAME'@'HOST';

查看授权

mysql>SHOW GRANTS FOR 'USERNAME'@'HOST';

EXAMPLE:

mysql>CREATE USER 'lujunyi'@'%' IDENTIFIED BY '123456';

mysql>SHOW GRANTS FOR 'lujunyi'@'%';

mysql>GRANT ALL PRIVILEGES ON testdb.* TO 'lujunyi'@'%';