Question

这是一个简单的问题，当我有（A，B）作为我的查询的结果时，我想只有（A，B），而不是（B，A）。

例如，我的查询返回：

这是我的问题：

SELECT S1.SURVEY_ID, S2.SURVEY_ID

  FROM SURVEYS S1, SURVEYS S2

  WHERE (S2.START_DATE BETWEEN S1.START_DATE and S1.END_DATE
  OR S2.END_DATE BETWEEN S1.START_DATE and S1.END_DATE)
  AND S1.SURVEY_ID != S2.SURVEY_ID

ORDER BY S1.SURVEY_ID, S2.SURVEY_ID

Answer 1

您可以使用条件排序将每个集(A,B) , (B,A)组合为一个组。

SELECT MAX(S1.SURVEY_ID) as survey_id_1, MIN(S2.SURVEY_ID) as survey_id_2
FROM SURVEYS S1
INNER JOIN SURVEYS S2
 ON (S2.START_DATE BETWEEN S1.START_DATE and S1.END_DATE
     OR S2.END_DATE BETWEEN S1.START_DATE and S1.END_DATE)
WHERE S1.SURVEY_ID != S2.SURVEY_ID
GROUP BY CASE WHEN S1.SURVEY_ID > S2.SURVEY_ID
              THEN S1.SURVEY_ID
              ELSE S2.SURVEY_ID
         END
ORDER BY survey_id_1, survey_id_2

这将导致（更大的调查，更小的调查） - 每组1个。

我还将您的连接语法更改为正确的连接语法，请尽量避免使用隐式连接语法（以逗号分隔）。

Answer 2

这是一种方法：

WITH SS as (
      SELECT S1.SURVEY_ID as SURVEY_ID1, S2.SURVEY_ID as SURVEY_ID2
      FROM SURVEYS S1 JOIN
           SURVEYS S2
           ON (S2.START_DATE BETWEEN S1.START_DATE and S1.END_DATE OR
               S2.END_DATE BETWEEN S1.START_DATE and S1.END_DATE
              ) AND
              S1.SURVEY_ID <> S2.SURVEY_ID
     )
SELECT ss.*
FROM ss
WHERE SURVEY_ID1 < SURVEY_ID2
UNION ALL
SELECT ss.*
FROM ss
WHERE SURVEY_ID1 > SURVEY_ID2 AND
      NOT EXISTS (SELECT 1 FROM ss ss2 WHERE ss2.SURVEY_ID1 = ss.SURVEY_ID2 AND ss2.SURVEY_ID2 = ss.SURVEY_ID1);

但是，如果您只是想要重叠调查，那么这将是适当的查询：

      SELECT S1.SURVEY_ID as SURVEY_ID1, S2.SURVEY_ID as SURVEY_ID2
      FROM SURVEYS S1 JOIN
           SURVEYS S2
           ON S2.START_DATE <= S1.END_DATE AND
              S2.END_DATE >= S1.START_DATE 
              S1.SURVEY_ID < S2.SURVEY_ID;

Answer 3

不确定我是否真的理解这个问题。猜猜：你希望（A，B）被视为（B，A）的副本，其中一个被删除。

将值放入一个订单（在降低之前更高），然后您可以使用distinct：

SELECT distinct 
  (CASE WHEN S1.SURVEY_ID > S2.SURVEY_ID THEN S1.SURVEY_ID ELSE S2.SURVEY_ID END) as "higher id",
  (CASE WHEN S1.SURVEY_ID > S2.SURVEY_ID THEN S2.SURVEY_ID ELSE S1.SURVEY_ID END) as "lower id"
...

如果我同时拥有（A，B）和（B，A），则只选择一对

3 个答案: