MySQL的七种JOIN
建表
在这里我们先建立两张有外键关联的两张表:
CREATE DATABASE db0206;
USE db0206;
CREATE TABLE `db0206`.`tbl_dept`(
`id` INT(11) NOT NULL AUTO_INCREMENT,
`deptName` VARCHAR(30),
`locAdd` VARCHAR(40),
PRIMARY KEY (`id`)
) ENGINE=INNODB CHARSET=utf8;
CREATE TABLE `db0206`.`tbl_emp`(
`id` INT(11) NOT NULL AUTO_INCREMENT,
`name` VARCHAR(20),
`deptId` INT(11),
PRIMARY KEY (`id`),
FOREIGN KEY (`deptId`) REFERENCES `db0206`.`tb_dept`(`id`)
) ENGINE=INNODB CHARSET=utf8;
/*插入数据*/
INSERT INTO tbl_dept(deptName,locAdd) VALUES('RD',11);
INSERT INTO tbl_dept(deptName,locAdd) VALUES('HR',12);
INSERT INTO tbl_dept(deptName,locAdd) VALUES('MK',13);
INSERT INTO tbl_dept(deptName,locAdd) VALUES('MIS',14);
INSERT INTO tbl_dept(deptName,locAdd) VALUES('FD',15);
INSERT INTO tbl_emp(NAME,deptId) VALUES('z3',1);
INSERT INTO tbl_emp(NAME,deptId) VALUES('z4',1);
INSERT INTO tbl_emp(NAME,deptId) VALUES('z5',1);
INSERT INTO tbl_emp(NAME,deptId) VALUES('w5',2);
INSERT INTO tbl_emp(NAME,deptId) VALUES('w6',2);
INSERT INTO tbl_emp(NAME,deptId) VALUES('s7',3);
INSERT INTO tbl_emp(NAME,deptId) VALUES('s8',4);
Venn图与SQL语句的编写以及查询结果
- 内连接
内连接Venn图
执行的SQL语句以及执行的查询结果:
- 执行的SQL语句
select * from tbl_dept a inner join tbl_emp b on a.id=b.deptId;
- 查询结果
- 左外连接
执行的sql语句以及执行的查询结果:
- 执行的sql语句
select * from tbl_dept a left join tbl_emp b on a.id=b.deptId;
- 查询结果
- 右外连接
执行的sql语句以及执行的查询结果:
- 执行的sql语句
select * from tbl_dept a right join tbl_emp b on a.id=b.deptId
- 查询结果
Enjoy Reading This Article?
Here are some more articles you might like to read next: