Question

让我们说我有一个User的Moder Posts。

所以现在例如我选择男性用户：

SELECT "users".* FROM "users" WHERE (gender = 'male')

如何扩展我的搜索查询并仅选择拥有带标记[sport,holiday]的帖子的男性用户？

如果我只需要使用Posts，我只需致电：

SELECT "posts".* FROM "posts" WHERE "posts"."tag" IN ('sport','holiday')

所以我尝试的是：

 SELECT "users".* FROM "users" INNER JOIN "posts" ON "posts"."user_id" = "users"."id" 
 WHERE "posts"."tag" IN ('sport', 'holiday') AND gender = 'male'

此搜索查询的问题在于，如果他有更多带有标签['sport'，'holiday']的帖子，则会多次返回相同的用户。我如何更改我的搜索查询，以便它只返回一次用户？感谢

Answer 1

尝试GROUP BY

GROUP BY users.id

或DISTINCT

Answer 2

SELECT DISTINCT "users".* FROM "users" INNER JOIN "posts" ON "posts"."user_id" = "users"."id" 
 WHERE "posts"."tag" IN ('sport', 'holiday') AND gender = 'male'

将返回唯一的行

或正如第一条评论所说，使用

组

SELECT "users".* FROM "users" INNER JOIN "posts" ON "posts"."user_id" = "users"."id" 
 WHERE "posts"."tag" IN ('sport', 'holiday') AND gender = 'male'
Group by users.id

Answer 3

您可以将IN运算符与子查询一起使用

SELECT "users".* 
FROM "users" 
WHERE "users"."id" IN (
    SELECT "posts"."user_id"
    FROM "posts"
    WHERE "posts"."tag" IN ('sport', 'holiday')
) AND gender = 'male'

或ANY

SELECT "users".* 
FROM "users" 
WHERE "users"."id" = ANY(
    (
     SELECT ARRAY(
         SELECT "posts"."user_id"
         FROM "posts"
         WHERE "posts"."tag" IN ('sport', 'holiday'))
     )::integer[]
) AND gender = 'male'

找到具有特定帖子SQL的所有男性用户

3 个答案: