MYSQL学习03--MySQL表操做、表链接

1. MySQL表数据类型

• 数值类型
  
• 日期和时间类型
  
• 字符串类型
  

2. 用SQL语句建立表

• 基本语法
  CREATE TABLE table_name (column_name column_type);

• 建立实例
  CREATE TABLE IF NOT EXISTS `courses`( `cid` INT UNSIGNED AUTO_INCREMENT, `student_name` VARCHAR(40) NOT NULL, `course_name` VARCHAR(40) NOT NULL, PRIMARY KEY (`cid`) )ENGINE = INNODB DEFAULT CHARSET= utf8;

  3. 用SQL语句向表中添加数据

• 基本语法
  

INSERT INTO table_name ( field1, field2,...fieldN )  
                       VALUES  
                       ( value1, value2,...valueN );

• 插入实例
  INSERT INTO salary(s_name,s_sex,salary) VALUES("张三","m",2500);

4. 用SQL语句删除表

• 基本语法
  DROP TABLE table_name ;
  
• 删除表的几种方式的不一样
  

1. DROP
   DROP TABLE table_name ;
   
2. TRUNCATE
   truncate table student;
   
3. DELETE
   delete from student where T_name = "张三";

5. 用SQL语句修改表

• 修改列名

• 修改表中数据

• 删除行

• 删除列

• 新建列

• 新建行

6. MySQL别名

• INNER JOIN

• LEFT JOIN

• CROSS JOIN

• 自链接

• UNION

• 以上几种方式的区别和联系

  0七、做业

• 项目3、超过5名学生的课
  建立以下所示的courses 表 ，有: student (学生) 和 class (课程)。
  

CREATE TABLE IF NOT EXISTS `courses`(  
    `cid` INT UNSIGNED AUTO_INCREMENT,  
    `student_name` VARCHAR(40) NOT NULL,  
    `course_name` VARCHAR(40) NOT NULL,  
    PRIMARY KEY (`cid`)  
)ENGINE = INNODB DEFAULT CHARSET= utf8;

插入数据 :

INSERT INTO courses(student_name,course_name) VALUES("张三","math");
INSERT INTO courses(student_name,course_name) VALUES("李四","English");
INSERT INTO courses(student_name,course_name) VALUES("王五","math");
INSERT INTO courses(student_name,course_name) VALUES("赵六","Biology");
INSERT INTO courses(student_name,course_name) VALUES("五天","math");
INSERT INTO courses(student_name,course_name) VALUES("刘八","math");
INSERT INTO courses(student_name,course_name) VALUES("孙慧","math");
INSERT INTO courses(student_name,course_name) VALUES("王伟","Computer");
INSERT INTO courses(student_name,course_name) VALUES("郑一","math");
INSERT INTO courses(student_name,course_name) VALUES("陈二","math");
INSERT INTO courses(student_name,course_name) VALUES("张一","Computer");
INSERT INTO courses(student_name,course_name) VALUES("张七","math");
INSERT INTO courses(student_name,course_name) VALUES("周天","English");

编写一个 SQL 查询，列出全部超过或等于5名学生的课，同一个学生不被重复计算。

SELECT course_name  
FROM   
    (SELECT DISTINCT student_name,course_name   
        from courses) aaa  
GROUP BY course_name  
HAVING COUNT(course_name)>5;

结果如图：

• 项目4、交换工资
  建立一个 salary表，以下所示，有m=男性 和 f=女性的值 。
  

CREATE TABLE IF NOT EXISTS `salary`(  
    `sid` INT UNSIGNED AUTO_INCREMENT,  
    `s_name` VARCHAR(40) NOT NULL,  
    `s_sex` VARCHAR(2) NOT NULL,  
    `salary` INT NOT NULL,  
    PRIMARY KEY (`sid`)  
)ENGINE = INNODB DEFAULT CHARSET= utf8;

插入数据：

INSERT INTO salary(s_name,s_sex,salary) VALUES("张三","m",2500);  
INSERT INTO salary(s_name,s_sex,salary) VALUES("李四","f",1500);  
INSERT INTO salary(s_name,s_sex,salary) VALUES("王五","m",5500);  
INSERT INTO salary(s_name,s_sex,salary) VALUES("赵六","f",500);  
INSERT INTO salary(s_name,s_sex,salary) VALUES("吴八","m",3500);

交换全部的 f 和 m 值:

UPDATE salary SET s_sex =IF(s_sex ="m","f","m");

• 项目5、组合两张表
  在数据库中建立表1和表2，并各插入三行数据（本身造）：
  

CREATE TABLE IF NOT EXISTS `person`(  
    `person_id` INT UNSIGNED AUTO_INCREMENT,  
    `first_name` VARCHAR(40) NOT NULL,  
    `last_name` VARCHAR(40) NOT NULL,  
    PRIMARY KEY(`person_id`)  
)ENGINE=INNODB DEFAULT CHARSET=utf8;

CREATE TABLE IF NOT EXISTS `address`(  
    `address_id` INT UNSIGNED AUTO_INCREMENT,  
    `person_id` INT UNSIGNED NOT NULL,  
    `city` VARCHAR(40) NOT NULL,  
    `state` VARCHAR(40) NOT NULL,  
    PRIMARY KEY(`address_id`),  
    FOREIGN KEY(`person_id`) REFERENCES person(`person_id`)  
)ENGINE=INNODB DEFAULT CHARSET=utf8;

插入数据：

INSERT INTO person(first_name,last_name) VALUES("jack","chen");  
INSERT INTO person(first_name,last_name) VALUES("tom","wang");  
INSERT INTO person(first_name,last_name) VALUES("cat","zhang");  
INSERT INTO person(first_name,last_name) VALUES("joy","chen");

INSERT INTO address(person_id,city,state) VALUES(1,"hubei","wuhan");  
INSERT INTO address(person_id,city,state) VALUES(2,"hunan","changsha");  
INSERT INTO address(person_id,city,state) VALUES(3,"sanxi","san");  
INSERT INTO address(person_id,city,state) VALUES(4,"beijing","canpin");

编写一个 SQL 查询，知足条件：不管 person 是否有地址信息，都须要基于上述两表提供 person 的如下信息：FirstName, LastName, City, State:

SELECT p.person_id,p.last_name,p.first_name,a.city,a.state   
from person p   
LEFT JOIN address a   
on p.person_id =a.person_id;

• 项目6、删除重复的邮箱
  编写一个 SQL 查询，来删除 email 表中全部重复的电子邮箱，重复的邮箱里只保留 Id 最小 的那个。
  建表省略。
  

DELETE FROM email where ID NOT IN (  
SELECT minid FROM(  
SELECT MIN(ID) as minid  
FROM email   
GROUP BY email) b  
);

参考：http://www.runoob.com/mysql/mysql-select-query.html