【MySQL高级】MySQL表的七种连接方式【提供演示SQL】

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🎯 本文详细介绍了SQL中七种JOIN的使用方法与应用场景，包括内连接、左连接、右连接、全连接以及独有部分的查询方式。通过具体示例和图形化展示，清晰解释了每种连接的结果及其SQL语句的编写方法。文章还提供了建表及数据插入的SQL代码，并通过实际操作演示了笛卡尔积、内连接、外连接等查询结果，帮助读者更好地理解连接的原理与实现。此外，针对MySQL不支持FULL OUTER JOIN的情况，提供了替代解决方案，如通过LEFT JOIN与RIGHT JOIN结合实现全连接效果。内容实用，适合SQL学习者深入掌握连接查询技巧。

文章目录

七种JOIN介绍练习建表+存储数据笛卡尔积内连接左连接（外连接）右连接（外连接）A表独有B表独有全连接实现方式一：左连接+右连接+公共部分去重实现方式二：左连接+B独有

A独有+B独有

七种JOIN介绍

图形连接方式说明SQL内连接共有部分SELECT FROM TableA A INNER JOIN TableB B ON A.Key = B.Key;左连接A表独有+共有部分SELECT FROM TableA A LEFT JOIN TableB B ON A.Key = B.Key;右连接B表独有+共有部分SELECT FROM TableA A RIGHT JOIN TableB B ON A.Key = B.Key;A的独有SELECT FROM TableA A LEFT JOIN TableB B ON A.Key = B.Key WHERE B.Key IS NULL;B的独有SELECT FROM TableA A RIGHT JOIN TableB B ON A.Key = B.Key WHERE A.Key IS NULL;全连接A的独有+共有部分+B的独有SELECT FROM TableA A FULL OUTER JOIN TableB B ON A.Key = B.Key; MySQL不支持FULL OUTER JOIN这种语法A独有+B独有SELECT FROM TableA A FULL OUTER JOIN TableB B ON A.Key = B.Key WHERE A.Key IS NULL OR B.Key IS NULL; MySQL不支持FULL OUTER JOIN这种语法

练习

建表+存储数据

CREATE TABLE `tbl_emp` (

`id` int(11) NOT NULL AUTO_INCREMENT,

`name` varchar(20) DEFAULT NULL,

`deptId` int(11) DEFAULT NULL,

PRIMARY KEY (`id`) ,

KEY `fk_dept_id`(`deptId`)

)ENGINE = InnoDB AUTO_INCREMENT = 1 CHARACTER SET = utf8;

CREATE TABLE `tbl_dept` (

`id` int(11) NOT NULL AUTO_INCREMENT,

`deptName` varchar(30) DEFAULT NULL,

`locAdd` varchar(40) DEFAULT NULL,

PRIMARY KEY (`id`)

) ENGINE = InnoDB AUTO_INCREMENT = 1 CHARACTER SET = utf8;

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);

insert into tbl_emp(NAME,deptId) values('s9',51);

笛卡尔积

select * from tbl_emp,tbl_dept;

5条数据和8条数据两两组合，一共40条，结果如下

"id" "name" "deptId" "id" "deptName" "locAdd"

"1" "z3" "1" "5" "FD" "15"

"1" "z3" "1" "4" "MIS" "14"

"1" "z3" "1" "3" "MK" "13"

"1" "z3" "1" "2" "HR" "12"

"1" "z3" "1" "1" "RD" "11"

"2" "z4" "1" "5" "FD" "15"

"2" "z4" "1" "4" "MIS" "14"

"2" "z4" "1" "3" "MK" "13"

"2" "z4" "1" "2" "HR" "12"

"2" "z4" "1" "1" "RD" "11"

"3" "z5" "1" "5" "FD" "15"

"3" "z5" "1" "4" "MIS" "14"

"3" "z5" "1" "3" "MK" "13"

"3" "z5" "1" "2" "HR" "12"

"3" "z5" "1" "1" "RD" "11"

"4" "w5" "2" "5" "FD" "15"

"4" "w5" "2" "4" "MIS" "14"

"4" "w5" "2" "3" "MK" "13"

"4" "w5" "2" "2" "HR" "12"

"4" "w5" "2" "1" "RD" "11"

"5" "w6" "2" "5" "FD" "15"

"5" "w6" "2" "4" "MIS" "14"

"5" "w6" "2" "3" "MK" "13"

"5" "w6" "2" "2" "HR" "12"

"5" "w6" "2" "1" "RD" "11"

"6" "s7" "3" "5" "FD" "15"

"6" "s7" "3" "4" "MIS" "14"

"6" "s7" "3" "3" "MK" "13"

"6" "s7" "3" "2" "HR" "12"

"6" "s7" "3" "1" "RD" "11"

"7" "s8" "4" "5" "FD" "15"

"7" "s8" "4" "4" "MIS" "14"

"7" "s8" "4" "3" "MK" "13"

"7" "s8" "4" "2" "HR" "12"

"7" "s8" "4" "1" "RD" "11"

"8" "s9" "51" "5" "FD" "15"

"8" "s9" "51" "4" "MIS" "14"

"8" "s9" "51" "3" "MK" "13"

"8" "s9" "51" "2" "HR" "12"

"8" "s9" "51" "1" "RD" "11"

内连接

SELECT * FROM tbl_emp a INNER JOIN tbl_dept b ON a.deptId = b.id;

左连接（外连接）

SELECT * FROM tbl_emp a LEFT JOIN tbl_dept b ON a.deptId = b.id;

右连接（外连接）

SELECT * FROM tbl_emp a RIGHT JOIN tbl_dept b ON a.deptId = b.id;

A表独有

SELECT * FROM tbl_emp a LEFT JOIN tbl_dept b ON a.deptId = b.id WHERE b.id is null;

B表独有

SELECT * FROM tbl_emp a RIGHT JOIN tbl_dept b ON a.deptId = b.id WHERE a.deptId is null;

全连接

尝试换一种方式实现：A的独有+共有+B的独有

实现方式一：左连接+右连接+公共部分去重

SELECT * FROM tbl_emp a LEFT JOIN tbl_dept b ON a.deptId = b.id

UNION

SELECT * FROM tbl_emp a RIGHT JOIN tbl_dept b ON a.deptId = b.id;

实现方式二：左连接+B独有

SELECT * FROM tbl_emp a LEFT JOIN tbl_dept b ON a.deptId = b.id

UNION

SELECT * FROM tbl_emp a RIGHT JOIN tbl_dept b ON a.deptId = b.id WHERE a.deptId is null;

A独有+B独有

SELECT * FROM tbl_emp a LEFT JOIN tbl_dept b ON a.deptId = b.id WHERE b.id is null

UNION

SELECT * FROM tbl_emp a RIGHT JOIN tbl_dept b ON a.deptId = b.id WHERE a.deptId is null;