Question

我对这个问题有一点脑力障碍，我发现很难找到解决方案，因为我无法正确地说出问题以提出相关信息。

我试图从下表中找回“fAroduct”记录，其中有“fAttribute” 2和20。

id  fAttribute  fProduct
19      2        2967
48      2        2923
50      2        3008
51      20       3008
52      2        2295
53      20       2295

如果我希望返回fProduct的2295和3008，我的下面的结果会产生0个结果。

SELECT fProduct 
FROM  tableName 
WHERE fAttribute = 2 AND fAttribute = 20
GROUP BY fProduct

有人可以帮忙吗？

Answer 1

您可以使用INNER JOINS或使用EXISTS条件：

INNER JOIN：

SELECT DISTINCT a.fProduct
FROM MyTable a
     INNER JOIN MyTable b ON a.fProduct = b.fProduct AND b.fAttribute = 2
     INNER JOIN MyTable c ON a.fProduct = c.fProduct AND c.fAttribute = 20

EXISTS：

SELECT afproduct
FROM MyTable a
WHERE EXISTS (SELECT b.id FROM MyTable b WHERE a.fProduct = b.fProduct AND b.fAttribute = 2)
  AND EXISTS (SELECT c.id FROM MyTable c WHERE a.fProduct = c.fProduct AND c.fAttribute = 20)

Answer 2

联接应该有所帮助：

SELECT distinct a.fProduct 
FROM  tableName as a
join tableName as b on b.product = a.product
WHERE a.fAttribute = 2 and  b.fAttribute = 20

Answer 3

由于您已经在进行GROUP BY，只需将WHERE子句更改为OR或IN，然后添加HAVING COUNT(fattribute) = 2即可确保它们同时存在。

SELECT fproduct 
FROM   tablename 
WHERE  fattribute IN (2 , 20)
GROUP  BY fproduct 
HAVING COUNT(fattribute) = 2

MySQL JOIN WHERE外键= id1 AND外键= id2

3 个答案: