当同一表的另一列的多个记录匹配时更新列

Question

我有如下表格：

            Input table:
            RequestNumber            TrackName         Date
            -----------------------------------------------------------
            02209                    Middle         2017-05-28 00:00:00
            0263                     Middle         2017-06-29 00:00:00
            0633                     Middle         2017-09-10 00:00:00
            0762                     Back           2017-06-23 00:00:00
            0762                     Front          2017-06-23 00:00:00
            0762                     Middle         2017-06-23 00:00:00
            01839                    Middle         2017-03-09 00:00:00

我需要检查“TrackName”的“RequestNumber”和“Date”是否相同。 如果“RequestNumber”和“Date”的多个reacords匹配，那么我应该将“TrackName”列更新为“All three”，如下所示 输出示例（本例中有 3 条记录匹配）

            Output table:
            RequestNumber            TrackName         Date
            -----------------------------------------------------------
            02209                    Middle         2017-05-28 00:00:00
            0263                     Middle         2017-06-29 00:00:00
            0633                     Middle         2017-09-10 00:00:00
            0762                     All three      2017-06-23 00:00:00
            01839                    Middle         2017-03-09 00:00:00

要获得上述设计的输出，这是我尝试过的 SQL。但是，它会将所有 TrackName 更新为全部三个。

            UPDATE a 
            SET a.[TrackName] = 'All three'
            FROM Table1 as a
            INNER JOIN 
            (SELECT [RequestNumber], row_number() OVER (ORDER BY [RequestNumber] DESC) as rowNumber
            FROM Table1 ) drRowNumbers ON drRowNumbers.[RequestNumber] = a.[RequestNumber] and drRowNumbers.[Date] = a.[Date]

希望我已经正确解释了这一点。我在做什么？请问有什么问题可以解决吗？

注意：记录是动态的，所以不能硬编码（如果有的话）。

谢谢。

Answer 1

试试这个。这将返回“All 3”而不是“All Three”-

SELECT RequestNumber,
CASE 
    WHEN COUNT(*) = 1 THEN MAX(TrackName) 
    ELSE 'All ' + CAST( COUNT(*) AS VARCHAR) 
END TrackName,
Date
FROM your_table
GROUP BY RequestNumber,Date

Answer 2

我想你想要SELECT 声明：

SELECT t1.RequestNumber, (CASE WHEN COUNT(DISTINCT t1.TrackName) = t2.TrackNo 
                               THEN CONCAT('All ', t2.TrackNo)  
                               ELSE MIN(t1.TrackName) 
                          END) AS TrackName, t1.Date
FROM table1 t1 CROSS JOIN
     (SELECT COUNT(DISTINCT TrackName) AS TrackNo FROM table1) AS t2
GROUP BY t1.RequestNumber, t1.Date;

Answer 3

这不仅仅是一次更新，也是一次删除。
这意味着您必须有一个两步过程 - 一个更新相关记录，然后删除第一步创建的重复项。

当两个步骤在事务中连接时，这可以使用几个使用窗口函数的公共表表达式来完成，例如 count() over() 和 row_number() over()。

首先，创建并填充示例表（请在您以后的问题中保存我们这一步）：

DECLARE @T AS TABLE
(
    RequestNumber int,
    TrackName varchar(10),
    [Date] datetime2
);

INSERT INTO @T (RequestNumber, TrackName, Date) VALUES
(02209, 'Middle', '2017-05-28 00:00:00'),
(0263, 'Middle', '2017-06-29 00:00:00'),
(0633, 'Middle', '2017-09-10 00:00:00'),
(0762, 'Back', '2017-06-23 00:00:00'),
(0762, 'Front', '2017-06-23 00:00:00'),
(0762, 'Middle', '2017-06-23 00:00:00'),
(01839, 'Middle', '2017-03-09 00:00:00');

接下来，启动一个try 块和一个事务：

BEGIN TRY
BEGIN TRANSACTION;

然后，识别并更新相关记录：

WITH CTE AS
(
    SELECT  RequestNumber, 
            TrackName, 
            Date,
            COUNT(TrackName) OVER(PARTITION BY RequestNumber, Date) As Cnt
    FROM @T
)

UPDATE CTE
SET TrackName = 'All Three'
WHERE Cnt = 3;

接下来，删除重复项：

WITH CTE AS
(
    SELECT  RequestNumber, 
            TrackName, 
            Date,
            ROW_NUMBER() OVER(PARTITION BY RequestNumber, Date ORDER BY TrackName) As Rn
    FROM @T
)

DELETE 
FROM CTE 
WHERE Rn > 1;

提交事务并关闭try 块：

COMMIT TRANSACTION;
END TRY

使用 catch 块回滚事务：

BEGIN CATCH
    IF @@TRANCOUNT > 0
        ROLLBACK TRANSACTION

    -- you might want to print the result of ERROR_MESSAGE() here...
END CATCH

最后，选择查看更改：

SELECT  RequestNumber, 
        TrackName, 
        Date
FROM @T

结果：

RequestNumber   TrackName   Date
2209            Middle      28.05.2017 00:00:00
263             Middle      29.06.2017 00:00:00
633             Middle      10.09.2017 00:00:00
762             All Three   23.06.2017 00:00:00
1839            Middle      09.03.2017 00:00:00

You can see a live demo on rextester（减去那里不允许的事务部分和无论如何没有事务不相关的 try...catch）

Answer 4

试试这个

第 1 步将其中一个记录设置为全部三个

update table1
set TrackName = 'All Three'
where requestnumber in (select requestnumber
from table1
group by requestnumber,[date]
having count(*) = 3)
and trackname = 'Front'

第 2 步删除不再需要的数据

delete table1
where requestnumber in (select requestnumber
from table1
group by requestnumber,[date]
having count(*) = 3)
and trackname <> 'All Three'