SQL SELF JOIN 消除重复值

Question

我必须 select 不同的月份 IS 下面的查询返回重复值。如何解决这个问题？

 SELECT DISTINCT m1.ID as C1, m2.ID as C2
    FROM Mois m1, Mois m2
    WHERE m1.ID IN('1','4','9')
    AND m2.ID IN('2','5','10')

这就是我想要得到的：

C1 |  C2 

1  |  2

4  |  5

9  |  10

Answer 1

SELECT MIN(C1),MIN(C2) FROM
(
    SELECT DISTINCT m1.ID as C1, m2.ID as C2,
    ROW_NUMBER() OVER (PARTITION BY m2.ID ORDER BY (SELECT 0)) AS ROWNUM
    FROM Mois m1
    INNER JOIN Mois m2
    ON m1.ID IN (1, 4, 9) AND
       m2.ID IN (2, 5, 10) AND
       m1.ID < m2.ID
) AS T1
GROUP BY ROWNUM

或

SELECT C1,C2 from
(SELECT DISTINCT m1.ID AS C1, 
    Row_number() over (Order by (SELECT 0)) AS RN
    FROM Mois m1
    WHERE m1.ID IN('1','4','9')) AS T1
INNER JOIN
(SELECT DISTINCT m2.ID AS C2,
    Row_number() over (Order by (SELECT 0)) AS RN
    FROM  Mois m2
    WHERE m2.ID IN('2','5','10')) AS T2
 ON T1.RN=T2.RN

输出

C1  C2
1   2
4   5
9   10

演示

http://sqlfiddle.com/#!18/f64e5/2

Answer 2

试试这个选项：

WITH cte1 AS (
    SELECT DISTINCT m1.ID as C1, m2.ID as C2
    FROM Mois m1
    INNER JOIN Mois m2
    ON m1.ID IN (1, 4, 9) AND
       m2.ID IN (2, 5, 10) AND
       m1.ID < m2.ID
),
cte2 AS (
    SELECT C1, C2, ROW_NUMBER() OVER (PARTITION BY C1 ORDER BY C2) rn
    FROM cte1
)

SELECT C1, C2
FROM cte2
WHERE rn = 1
ORDER BY C1;

C1   C2
1   1   2
2   4   5
3   9   10

Demo