
A right join B
|:连接的记录数与B表的记录数同(显示B表的所有记录 ,A表不存在记录则为NULL)
A left join B |: 等价B right join A
A inner join B |: 两个表相匹配的记录出现在查询结果列表中
提示:
select * from a,b where a.Field_K=b.Field_K
|联表查询 :这个语法是内连接的另外一种写法,其执行结果与inner join 一样 ;
提示 :left join是left outer join的简写 ,查询结果一样;



Field_K, Field_A








4 z








4 c 4 z








4 c 4 z
---------------------------------------------------------------------------------------------------------------------------------------
select a.Field_K, a.Field_A, b.Field_K, b.Field_B
from a inner join b on a.Field_K=b.Field_K
Field_K Field_A Field_K Field_B
---------- ---------- ---------- ----------
1 a 1 x
4 c 4 z