选择与连接表中的所有选定行匹配的行

Question

我有一个条目表和一个类别表,其中一个连接表将两者联系起来,我想要做的是选择与特定类别集匹配的所有条目.

例如.所有具有A类和B类的条目

项

entry_id | title
------------------
1        | Entry 1
2        | Entry 2
3        | Entry 3

类别

category_id | name
------------------
1           | A
2           | B
3           | C

entry_categories

entry_id | category_id
-----------------------
1        | 1
1        | 2
2        | 1
2        | 2
2        | 3
3        | 1
3        | 3

如果我这样做,我会得到所有3个条目,因为它们每个都至少匹配一个类别,但我真正想要的是条目1和条目2而不是条目3.

SELECT *
FROM entry_categories AS ec
INNER JOIN entries AS e ON ec.entry_id = e.entry_id
WHERE ec.category_id IN(1, 2)
GROUP BY e.entry_id

Answer 1

HAVING COUNT(ec.Categor_id) = 2像这样添加:

SELECT *
FROM entry_categories AS ec
INNER JOIN entries AS e ON ec.entry_id = e.entry_id
WHERE ec.category_id IN(1, 2)
GROUP BY e.entry_id
HAVING COUNT(ec.Category_id) = 2