MySQL left join right join inner join 差异

mysql left join right join inner join 区别

请看下面的语句

注意比较06 和07的显示结果，自己测试的 语法没有错误

— left join , right join ,inner join 实验

CREATE DATABASE if NOT EXISTS join_test;
use join_test;
DROP TABLE If EXISTS tbl_a;
create table tbl_a (
id int(11) auto_increment primary key,
name varchar(255),
email varchar(255)
);

DROP TABLE If EXISTS `tbl_b`;
create table `tbl_b`(
`id` int(11) auto_increment primary key,
`name` varchar(255),
`email` varchar(255)
);
use join_test;
— inset into tbl_a
insert into tbl_a values(1,’a_name_001′,’a_email_001′);
insert into tbl_a values(2,’a_name_002′,’a_email_002′);
insert into tbl_a values(3,’a_name_003′,’a_email_003′);
insert into tbl_a values(4,’a_name_004′,’a_email_004′);
insert into tbl_a values(5,’a_name_005′,’a_email_005′);
insert into tbl_a values(7,’a_name_007′,’a_email_007′);

— insert into tbl_b
insert into tbl_b values(1,’b_name_001′,’b_email_001′);
insert into tbl_b values(2,’b_name_002′,’b_email_002′);
insert into tbl_b values(3,’b_name_003′,’b_email_003′);
insert into tbl_b values(4,’b_name_004′,’b_email_004′);
insert into tbl_b values(5,’b_name_005′,’b_email_005′);
insert into tbl_b values(6,’b_name_006′,’b_email_006′);

— left join
select * from tbl_a left join tbl_b on tbl_a.id=tbl_b.id;

查询结果：

1

2

3

4

5

— right join
select * from tbl_a right join tbl_b on tbl_a.id=tbl_b.id;
查询结果：

1

2

3

4

5

6

— inner join
select * from tbl_a inner join tbl_b on tbl_a.id=tbl_b.id
查询结果：

1

2

3

4

5

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