MySQL加入多个条件

Question

我有一个sql查询的问题,实际上是一个简单的查询,但我无法弄清楚我错过了什么,所以我来找你的帮助...所以,我要做什么

我有两个表rooms和rooms facilities......我不得不选择与所希望的设施客房..

如果我选择一个房间有一个设施(设施id = 4 - id_fu - )...使用以下查询

SELECT u.* FROM rooms u 
JOIN facilities_r fu 
ON fu.id_uc = u.id_uc 
    AND fu.id_fu = '4' 
WHERE 1 
    AND vizibility='1' 
GROUP BY id_uc 
ORDER BY u_premium desc, id_uc DESC 

一切安好.

但是,如果我想选择具有更多设施的房间,让我们说id = 4,id = 3的设施..使用以下查询

SELECT u.* FROM room u 
JOIN facilities_r fu 
ON fu.id_uc=u.id_uc 
    AND fu.id_fu = '4' 
    AND fu.id_fu = '3' 
WHERE 1 
    AND vizibility = '1' 
GROUP BY id_uc 
ORDER BY u_premium DESC, id_uc DESC 

它不起作用.

我无法理解为什么它不起作用,但我无法弄清楚如何处理这个条件......

谢谢,Mihai

Answer 1

您可以使用括号对条件进行分组.当您检查字段是否等于另一个字段时,您想要使用OR.例如WHERE a='1' AND (b='123' OR b='234').

SELECT u.*
FROM rooms AS u
JOIN facilities_r AS fu
ON fu.id_uc = u.id_uc AND (fu.id_fu='4' OR fu.id_fu='3')
WHERE vizibility='1'
GROUP BY id_uc
ORDER BY u_premium desc, id_uc desc

Answer 2

SELECT 
    u . *
FROM
    room u
        JOIN
    facilities_r fu ON fu.id_uc = u.id_uc
        AND (fu.id_fu = '4' OR fu.id_fu = '3')
WHERE
    1 and vizibility = '1'
GROUP BY id_uc
ORDER BY u_premium desc , id_uc desc

你必须在这里使用OR,而不是AND.

由于id_fu不能同时等于4和3.

Answer 3

如果您两次加入设施表,您将获得以下内容:

select u.* 
from room u 
  JOIN facilities_r fu1 on fu1.id_uc = u.id_uc and fu1.id_fu = '4'
  JOIN facilities_r fu2 on fu2.id_uc = u.id_uc and fu2.id_fu = '3' 
where 1 and vizibility='1' 
group by id_uc 
order by u_premium desc, id_uc desc