MySQL 查询问题?

Question

A表

id	name
1	a
2	b

B表

id	name
1	aa
2	bb

C表

id	name
1	aaa
2	bbb

D表

id	a_id	b_id	c_id
1	1	2	1
2	0	0	2
3	2	0	2

SELECT d.id, a.name AS a_name, b.name AS b_name, c.name AS c_name
FROM D AS d, A AS a, B AS b, C AS c
WHERE d.a_id = a.id AND d.b_id = b.id AND d.c_id = c.id

现在只要D表有0，就查询不出整条记录，怎么能查出全部，如果D表没有关联的那name就为空

Answer 1

仅供参考

select d.id, a.name as a_name, b.name as b_name, c.name as c_name
from D as d
left join A as a on a.id=d.a_id
left join B as b on b.id=d.b_id
left join C as c on c.id=d.c_id