数据库的内连接，左外连接，右外连接的区别

数据库的内连接，左外连接，右外连接的区别，

表a

aid aname

1    a1

2    a2

3    a3

表b

bid bname

1    b1

2    b2

4    b4

内联：select * from a inner join b on a.aid=b.bid

result:

1 a1 b1

2 a2 b2

左联：select * from a left join b on a.aid=b.bid

result:

1 a1 b1

2 a2 b2

3 a3 空字符

右联:select * from a right join b on a.aid=b.bid

result:

1 a1 b1

2 a2 b2

4 空字符 b4