選擇一條記錄中條件為真的記錄

Question

我需要從下表的行中選擇cid，項目和所有者，其中cid /項目組合的一或多個行的所有者為1。

cid | project | phase | task | owner
-----------------------------------
1   | 1       | 1     | 1    | 1
1   | 1       | 1     | 2    | 2
1   | 1       | 1     | 3    | 2
2   | 1       | 1     | 1    | 1
2   | 1       | 1     | 2    | 1
3   | 1       | 1     | 3    | 2

我的輸出表應如下所示：

cid | project | phase | task | owner
-----------------------------------
1   | 1       | 1     | 1    | 1
1   | 1       | 1     | 2    | 2
1   | 1       | 1     | 3    | 2
2   | 1       | 1     | 1    | 1
2   | 1       | 1     | 2    | 1

下面的查詢是我想出的。 看來確實可以，但是我的信心很低。 查詢是解決問題的有效方法嗎？

select task1.cid, task1.project, task1.owner
from 
(select cid, project, owner from table) task1
right join 
(select distinct cid, project, owner from table where owner = 1) task2
on task1.cid = task2.cid and task1.project = task2.project

（我沒有從示例輸出中刪除階段和任務列，以便於比較。）

Answer 1

您可以簡單地使用IN子句

  select cid, project, owner
  from table
  where cid in (select distinct id from table where owner = 1)

或帶有子查詢的內部聯接

  select a.cid, a.project, a.owner
  from table a 
  INNER JOIN ( select distinct cid , project
        from table where owner = 1
  ) t on t.cid = a.cid and t.project = a.project