MYSQL基本操作语句

0、修改密码:mysqladmin -u root -p password 123456

导出数据库：mysqldump -u root -p yunpay>yunpay.sql

导入数据库：mysql –u root -p yunpay < yunpay.sql

1、为mysql增加一个名为admin，主机名任意的网络用户，其通过密码'123'访问数据库，这个用户拥有对数据库的所有操作权限（ALL PRIVILEGES）

CREATE USER 'admin'@'%' IDENTIFIED BY '123';

GRANT ALL PRIVILEGES ON * . * TO 'admin'@'%' IDENTIFIED BY '123' WITH GRANT OPTION;

2、删除该用户

DROP USER 'wbhuang'@'%';

3、创建数据库

CREATE DATABASE school;

USE school;

SHOW TABLES;

4、删除、创建数据表

删除数据表时，有如下语法

DROP TABLE <表名> [RESTRICT | CASCADE];

当选择RESTRICT：则该表的删除是有限制条件的。欲删除的基本表不能被其他表的约束所引用（如CHECK，FOREIGN KEY等约束），不能有视图，触发器，存储过程和函数，否则不能删除。如果选择CASCADE：则删除基本表的同事，相关的依赖对象，例如视图，都将被一起删除。下面语句的"SET FOREGIN_KEY_CHECKS = 0;"为取消CHECKS依赖。可见MYSQL默认的删除表方式为RESTRICT（受约束的）。

SET FOREIGN_KEY_CHECKS = 0;

DROP TABLE IF EXISTS Student;

DROP TABLE IF EXISTS Course;

DROP TABLE IF EXISTS SC;

 

CREATE TABLE Student

    (Sno CHAR(9) PRIMARY KEY,

     Sname CHAR(20) UNIQUE,

         Ssex CHAR(2),

         Sage SMALLINT,

         Sdept CHAR(20)

        );

         

CREATE TABLE Course

    (Cno CHAR(4) PRIMARY KEY,

         Cname CHAR(40),

         Cpno CHAR(4),/*先修课*/

         Ccredit SMALLINT,

         FOREIGN KEY (Cpno) REFERENCES Course(Cno)

         /*表级完整性约束条件，Cpno是外码，被参照表是Course，被参照列是Cno*/

         );

 

CREATE TABLE SC

    (Sno CHAR(9),

         Cno CHAR(4),

         Grade SMALLINT,

         PRIMARY KEY (Sno,Cno),

         /*主码由两个属性构成，必须作为表级完整性进行定义*/

         FOREIGN KEY (Sno) REFERENCES Student(Sno),

         FOREIGN KEY (Cno) REFERENCES Course(Cno)

        );

5、修改数据表

ALTER TABLE Student DROP COLUMN Sentry;

ALTER TABLE Student ADD Sentrance DATE;

ALTER TABLE Student CHANGE Sentrance Sentry DATE;

/*为Student增加"入学时间"列*/

 

ALTER TABLE Student MODIFY COLUMN Sage INT;

/*将年龄的数据类型由字符型改为整形*/

 

ALTER TABLE Course ADD UNIQUE(Cname);

/*增加课程名称必须取唯一值的约束条件*/

6、删除、创建索引表

DROP INDEX Stusno ON Student;

DROP INDEX Coucno ON Course;

DROP INDEX SCno ON SC;

 

CREATE UNIQUE INDEX Stusno ON Student(Sno);

/*按课程号升序建唯一索引*/

CREATE UNIQUE INDEX Coucno ON Course(Cno);

/*SC表按学号升序和课程号降序建唯一索引*/

CREATE UNIQUE INDEX SCno ON SC(Sno ASC, Cno DESC);

<br>SELECT * FROM INDEX Stusno;

7、插入数据

INSERT INTO Student (Sno,Sname,Ssex,Sage,Sdept,Sentry) VALUES('20071025','wbhuang','male',23,'math','2007-09-01');

INSERT INTO Student (Sno,Sname,Ssex,Sage,Sdept,Sentry) VALUES('20071026','dkluo','male',24,'math','2007-09-01');

INSERT INTO Student (Sno,Sname,Ssex,Sage,Sdept,Sentry) VALUES('20071005','hlyang','male',24,'math','2007-09-01');

INSERT INTO Student (Sno,Sname,Ssex,Sage,Sdept,Sentry) VALUES('20071007','ljhu','male',24,'math','2007-09-01');

INSERT INTO Student (Sno,Sname,Ssex,Sage,Sdept,Sentry) VALUES('20071024','yluo','male',24,'math','2007-09-01');

INSERT INTO Course (Cno,Cname,Cpno,Ccredit) VALUES('100','Chinese','100',4);

INSERT INTO Course (Cno,Cname,Cpno,Ccredit) VALUES('101','English','100',3);

INSERT INTO Course (Cno,Cname,Cpno,Ccredit) VALUES('102','Science','100',2);

INSERT INTO Course (Cno,Cname,Cpno,Ccredit) VALUES('103','Math','100',5);

8、修改、删除数据

UPDATE  `school`.`student` SET  `Sname` =  'wbhuang',`Sdept` =  'xinji' WHERE  `student`.`Sno` =  '20071025';

DELETE FROM Student WHERE Sno='20071025';

9、普通查询和聚集函数

SELECT Sno,Sname,Ssex FROM Student WHERE Sno='20071004';

SELECT COUNT(DISTINCT Sname) FROM Student;

SELECT AVG(Sage) FROM Student;

SELECT Cno FROM Student ORDER BY Sage DESC;

 

ORDER BY <列名|,列名> [ASC | DESC];       ASC升序，DESC降序

COUNT([DISTINCT | ALL] * )          统计元素个数

COUNT([DISTINCT | ALL] <列名> ) 统计一列中元素个数

SUM([DISTINCT | ALL] <列名> )       计算一列值的总和（数值型）

AVG([DISTINCT | ALL] <列名> )       计算一列值的平均值（数值型）

MAX([DISTINCT | ALL] <列名> )       计算一列值的最大值

MIX([DISTINCT | ALL] <列名> )       计算一列值的最小值

 

GROUP BY 子句将查询结果按某一列或多列的值分组，值相等的为一组。

SELECT Cno,COUNT(Sno) FROM SC GROUP BY Cno;

/*Cno值相等的为一组，计算各组的COUNT(Sno)*/

10、连接查询

/*等值，非等值连接：比较的连接谓词有=、<、>、>=、<=、!=(或<>)等*/

SELECT Student.*,SC.* FROM Student,SC WHERE Student.Sno=SC.Sno;

/*若在等值连接中把目标列的重复的属性去掉则为自然连接*/

SELECT Student.*,SC.Cno,SC.Grade FROM Student,SC WHERE Student.Sno=SC.Sno;

/*自身连接：一个表与自己进行连接*/

SELECT FIRST.*,SECOND.* FROM Course FIRST, Course SECOND WHERE FIRST.Cpno=SECOND.Cno;

/*外连接：若某个Student没有选课，仍把舍弃的Student元组保存在结果中，其SC的属性全填NULL*/

SELECT * FROM Student LEFT JOIN SC ON (Student.Sno=SC.Sno);

11、嵌套查询

/*去掉Student.Cname的UNIQUE*/

ALTER TABLE Student DROP INDEX Sname;

 

/*带有比较运算符的子查询*/

SELECT Sno,Sname,Sdept

FROM Student

WHERE Sdept = (

    SELECT Sdept

    FROM Student

    WHERE Sno='20071004');

                         

SELECT Sno,Sname,Sdept

FROM Student

WHERE Sno IN (

    SELECT Sno

    FROM SC

    WHERE Grade>=5);

                         

/*带有ANY(SOME)或ALL谓词的子查询*/                          

SELECT Sno,Sname,Sage,Ssex

FROM Student

WHERE Sage>ANY (

    SELECT Sage

    FROM Student

    WHERE Ssex='fe');

 

/*带有[NOT] EXISTS谓词的子查询*/

/*EXISTS谓词的子查询不反悔任何数据，只产生逻辑真与假*/

/*拿外层的元组逐个放在内层中判断是否EXIST，如果为真则将元组放入结果集*/

SELECT Sname

FROM Student

WHERE EXISTS (

    SELECT *

    FROM SC

    WHERE Sno=Student.Sno

    AND Cno='100');

                             

/*集合查询：UNION并集，INTERSECT交集，EXCEPT差集*/

SELECT Sno

FROM Student

WHERE Sdept='hwx'

UNION

SELECT *

FROM Student

WHERE Sage>=20;

12、视图操作

/*创建视图*/

CREATE VIEW V_Student

AS

SELECT Sno,Sname,Sage

FROM Student

WHERE Sdept='xj';

 

/*删除视图*/

DROP VIEW V_Student;

 

/*查询视图*/

SELECT Sno,Sname

FROM V_Student

WHERE Sage>50;

 

/*更新视图*/

UPDATE V_Student

SET Sname='vname'

WHERE Sno='20071089';

 

INSERT INTO V_Student

VALUES ('20081010','vnew',36);