Question

我有两张桌子：

页面表包含字段id

pages2categories表包含字段page和category

我想从页面表中选择记录

where (there is a record in the pages2categories table 
WHERE pages2categories::page = pages::id AND pages2categories:: category = 'X') 
AND (there is also a record in the pages2categories table WHERE pages2categories::page = pages::id AND pages2categories:: category = 'Y') 
AND (there is also a record in the pages2categories table WHERE pages2categories::page = pages::id AND pages2categories:: category = 'Z')

换句话说，只有在pages2categories表中存在所有三个匹配记录时，才从页面表中返回记录。

实施例

信息页:: ID

pages2categories :: page，pages2categories :: category

1, x

1, y

2, x

2, y

2, z

3, x

结果应该只从页面表中返回记录2。

我希望这很清楚。谢谢！

Answer 1

在你的问题中你写道：

换句话说，只有在pages2categories表中存在所有三个匹配记录时，才从页面表中返回记录。

您还写道，查询应返回包含您提供的示例数据的2行，但根据您的数据，只有一行包含所有3个类别（第2页）。

所以，我不确定我是否正确理解它，但这是实现它的一种方法：

SELECT p.* FROM page p
LEFT JOIN pages2categories cx ON (cx.page = p.id AND cx.category = 'x')
LEFT JOIN pages2categories cy ON (cy.page = p.id AND cy.category = 'y')
LEFT JOIN pages2categories cz ON (cz.page = p.id AND cz.category = 'z')
WHERE cx.category IS NOT NULL
AND  cy.category IS NOT NULL
AND  cz.category IS NOT NULL

Answer 2

select id from table
group by id
where count(distinct category) = (select count(distinct category) from table)

Answer 3

您也可以使用：

SELECT * FROM TABLE1 A
WHERE EXISTS (SELECT * FROm TABLE2 B WHERE A.ID = B.ID AND B.category = 'X') 
AND EXISTS (SELECT * FROm TABLE2 B WHERE A.ID = B.ID AND B.category = 'Y')
AND EXISTS (SELECT * FROm TABLE2 B WHERE A.ID = B.ID AND B.category = 'Z')

MySQL选择相关表中有多个匹配记录的记录

3 个答案: