如何跨多行查询匹配值？

Question

我有2个表：通过player_tags加入的玩家和标签。我想让玩家Aaron只有匹配1个或更多标签名称。在我的情况下，我希望所有玩家都有标记＆＃34; test＆＃34;和＆＃34;新＆＃34;但由于它们属于两排，我不知道该怎么做。

table: players
ID    NAME
----- --------
1     AARON
2     JAMES


table: player_tags
ID    PLAYER_ID TAG_ID
----- --------- --------
1     1         1
2     1         2
3     2         1


table: tags
ID    NAME
----- --------
1     test
2     new

我创建了这个查询当然不起作用，因为标签＆＃39;测试＆＃39;并标记＆＃39; new＆＃39;分为2个不同的行。

SELECT "players".name, "tags".name FROM "players"
  INNER JOIN "player_tags" ON "player_tags"."player_id" = "players"."id" 
  INNER JOIN "tags" ON "tags"."id" = "player_tags"."tag_id"
WHERE
  "tags"."name" IS NOT NULL AND "tags"."name" = 'test' AND "tags"."name" = 'new'

我希望将播放器1作为响应，因为它匹配两个标签。如果我改变了＆＃39; AND＆＃39;到＆＃39;或者＆＃39;好吧，我得到了两个球员，但这不是我想要的。我使用postgres BTW。

Answer 1

select p.name as player_name, string_agg(t.name, ', ') as tags
from players p
  join player_tags pt ON pt.player_id = p.id 
  join tags t ON t.id = pt.tag_id
where t.name in ('new', 'test')
group by p.name
having count(t.id) > 1

上面实现了“如果它匹配一个或多个标签名称”部分，那么它将返回那些至少其中一个标签的玩家。

如果您只想要那些拥有这两个标签的玩家，您可以使用：

select p.name as player_name, string_agg(t.name, ', ') as tags
from players p
  join player_tags pt ON pt.player_id = p.id 
  join tags t ON t.id = pt.tag_id
group by p.name
having array_agg(t.name order by t.name) = array['new', 'test']

请注意，您需要按字母顺序指定数组中的标记名称。

在线示例：

Answer 2

试试这个，我还没有postgres进行测试，告诉我是否存在语法错误。

在ARRAY['test', 'new']中，您可以添加所需的标记名称。

select player, array_agg(tag) as tags from (
    SELECT players.name AS player, tags.name AS tag FROM players
    INNER JOIN player_tags
    ON players.ID = player_tags.PLAYER_ID 
    INNER JOIN tags
    ON player_tags.TAG_ID = tags.ID
) t
group by player
having
ARRAY(SELECT unnest(array_agg(tag)) ORDER BY 1)  = ARRAY(SELECT unnest(ARRAY['test', 'new']) ORDER BY 1) 

Answer 3

我对postgresql不熟悉，但是你可以为你正在寻找的每个标签加入一次播放器标签表吗？

在SQL Server中，我可以执行以下操作：

select p.name
from players p 
join player_tags pt1 on p.id = pt1.player_id and pt1.tag_id = 1
join player_tags pt2 on pt1.player_id = pt2.player_id and pt2.tag_id = 2

你能做那样的事吗？

Answer 4

您必须确保两个条件都成立：

with ctag as
(
    select pt.player_id pid, t.name tname
    from players_tags pt 
         inner join tags t on t.id = pt.tag_id
    where tags.name in ('test','new')
)
select p.id, p.name
from players p
where exists (select 1 from ctag where pid = p.id and tname = 'test')
      and exists (selet 1 from ctag where pid = p.id and tname = 'new');