如何使用带有ORDER BY的DISTINCT关键字

Question

我有一个带值的表

 ID  Number
 1    6
 2    6
 3    7
 4    7
 5    1
 6    1
 7    2
 8    2

我为不同的数字写了一个选择查询

SELECT DISTINCT Number FROM Table 

我的输出就像

 ID  Number
 1    1
 2    2
 3    6
 4    7

但我想输出

ID  Number
 1    6
 2    7
 3    1
 4    2

我怎样才能带来这样的输出？

Answer 1

您可以使用ROW_NUMBER等窗口函数：

WITH cte AS
(
  SELECT Number, MAX(ID) AS max_ID
  FROM #Tab
  GROUP BY Number
)
SELECT ROW_NUMBER() OVER(ORDER BY max_ID) AS ID, Number
FROM cte
ORDER BY max_ID

的 LiveDemo

输出：

╔════╦════════╗
║ ID ║ Number ║
╠════╬════════╣
║  1 ║      6 ║
║  2 ║      7 ║
║  3 ║      1 ║
║  4 ║      2 ║
╚════╩════════╝

Answer 2

因此，您要删除重复的Numbers并按ID保留排序。

一种可能的方法是使用ROW_NUMBER：

DECLARE @T TABLE ([ID] int, [Number] int);

INSERT INTO @T ([ID], [Number]) VALUES
    (1, 6),
    (2, 6),
    (3, 7),
    (4, 7),
    (5, 1),
    (6, 1),
    (7, 2),
    (8, 2);

WITH
CTE
AS
(
    SELECT
        ID
        ,Number
        ,ROW_NUMBER() OVER (PARTITION BY Number ORDER BY ID) AS rn
    FROM @T AS T
)
SELECT
    ID
    ,Number
FROM CTE
WHERE rn = 1
ORDER BY ID;

<强>结果

ID  Number
1   6
3   7
5   1
7   2