Question

我有以下数据

COL-1     COL-2

1        0TY/OK
1        0TY/OK
1        0TY/OK 
1        0TY/OK 
1        0TY/OK
2        2KP/L         
2        2KP/L
2        2KP/L  
2        2KP/L       
2        2KP/L      
3        7U5/2M
3        7U5/2M 
3        7U5/2M 
3        7U5/2M

我想构建一个select查询以在

下面的输出中检索该数据

COL-1     COL-2        COL-3

1        0TY/OK      0TY/OK
1        0TY/OK      2KP/L  
1        0TY/OK      7U5/2M
1        0TY/OK 
1        0TY/OK
2        2KP/L         
2        2KP/L
2        2KP/L  
2        2KP/L       
2        2KP/L      
3        7U5/2M
3        7U5/2M 
3        7U5/2M 
3        7U5/2M

我希望COL3返回COL2的不同值

使用SELECT COL1, COL2, DISTINCT COL2 AS COL3 FROM MYTable不起作用是SQL SERVER

Answer 1

虽然我确信某些SQL向导能够构建一种方法来执行此操作，但我觉得需要指出概念上这没有意义 - 第3列的行中的值完全不相关到第1列和第2列中的行值。

您是否可以在单独的查询中简单地返回COL2的不同值？

SELECT DISTINCT COL2 FROM MyTable

（请注意，您可以从单个SQL查询返回多个结果集）

Answer 2

这是非常不寻常的，我无法理解为什么你想在一个结果集中使用它，因为它没有任何意义......没有理由将不同查询的行与非结果中的行相关联-distinct query。，但你要做的只是运行两个查询

Select Col1, Col2 From Table
Order By Col1, Col2

并且

Select Distinct Col2 From Table

并将它们连接在一起（要在行号上加入它们，请为每个查询添加一个Row_Number（）函数：

   Select Col1, Col2, Col3
   From   (Select Row_Number() Over(Order By Col1, Col2)RowNum, 
               Col1, Col2 
           From Table) T1
     Left Join 
          (Select Distinct Col2 As Col3,
           (Select Count(Distinct Col2)
            From Table
            Where Col2 <= T2.Col3) RowNum                    
           From Table) T2
        On T2.RowNum = T1.RowNum

Answer 3

您可以使用CTE在这些虚拟列上创建ROW_NUMBER和JOIN。

DECLARE @t TABLE (
   Col1 INT
   ,Col2 VARCHAR(10)
);

INSERT INTO @t VALUES (1, '0TY/OK');
INSERT INTO @t VALUES (1, '0TY/OK');
INSERT INTO @t VALUES (1, '0TY/OK');
INSERT INTO @t VALUES (1, '0TY/OK');
INSERT INTO @t VALUES (1, '0TY/OK');
INSERT INTO @t VALUES (2, '2KP/L,');
INSERT INTO @t VALUES (2, '2KP/L');
INSERT INTO @t VALUES (2, '2KP/L');
INSERT INTO @t VALUES (2, '2KP/L');
INSERT INTO @t VALUES (2, '2KP/L');
INSERT INTO @t VALUES (3, '7U5/2M');
INSERT INTO @t VALUES (3, '7U5/2M');
INSERT INTO @t VALUES (3, '7U5/2M');
INSERT INTO @t VALUES (3, '7U5/2M');

; WITH all_data AS (
   SELECT
      Col1
      ,Col2
      ,ROW_NUMBER() OVER (ORDER BY (SELECT 1)) AS RowNum
   FROM @t
),
distinct_data AS (
   SELECT
      Col2
      ,ROW_NUMBER() OVER (ORDER BY (SELECT 1)) AS RowNum
   FROM @t
   GROUP BY
      Col2
)
SELECT
   all_data.Col1
   ,all_data.Col2
   ,distinct_data.Col2
FROM all_data
   LEFT JOIN distinct_data ON all_data.RowNum = distinct_data.RowNum

Answer 4

试试这个..

WITH MyTable AS
(
    SELECT 1 Col1,CONVERT (VarChar (25), '0TY/OK') Col2 UNION ALL
    SELECT 1,'0TY/OK' UNION ALL
    SELECT 1,'0TY/OK' UNION ALL
    SELECT 1,'0TY/OK' UNION ALL
    SELECT 1,'0TY/OK' UNION ALL
    SELECT 2,'2KP/L' UNION ALL
    SELECT 2,'2KP/L' UNION ALL
    SELECT 2,'2KP/L' UNION ALL
    SELECT 2,'2KP/L' UNION ALL
    SELECT 2,'2KP/L' UNION ALL
    SELECT 3,'7U5/2M' UNION ALL
    SELECT 3,'7U5/2M' UNION ALL
    SELECT 3,'7U5/2M' UNION ALL
    SELECT 3,'7U5/2M'
)
,
AllData AS
(
    SELECT 
        *, 
        ROW_NUMBER () OVER (ORDER BY Col2) as Id
    FROM MyTable
)
,
DistinctData AS
(
        SELECT 
            Distinct Col2 AS Col3
        FROM MyTable
),
DistinctWithRowNumber AS
(
    SELECT 
        *, 
        ROW_NUMBER () OVER (ORDER BY Col3) as Id
    FROM DistinctData
)
SELECT 
    Col1, 
    Col2, 
    Col3
FROM AllData
    LEFT JOIN DistinctWithRowNumber 
        ON AllData.Id = DistinctWithRowNumber.Id

返回此结果

Col1        Col2                      Col3
----------- ------------------------- -------------------------
1           0TY/OK                    0TY/OK
1           0TY/OK                    2KP/L
1           0TY/OK                    7U5/2M
1           0TY/OK                    NULL
1           0TY/OK                    NULL
2           2KP/L                     NULL
2           2KP/L                     NULL
2           2KP/L                     NULL
2           2KP/L                     NULL
2           2KP/L                     NULL
3           7U5/2M                    NULL
3           7U5/2M                    NULL
3           7U5/2M                    NULL
3           7U5/2M                    NULL

尝试过滤重复项时出现T-SQL Distinct列问题

4 个答案: