SQL 服务器合并数据集

Question

我有一个查询 return 是一个如下所示的数据集：

Region                           Name
-------------------------------------------------------------
Canada                           Jim 
Canada                           Michael
Canada                           Andy
Mexico                           Jim
Mexico                           Michael
Mexico                           Kevin

但我想 return 改成这样：

Region                           Name
-------------------------------------------------------------
Canada, Mexico                   Jim
Canada, Mexico                   Michael
Canada                           Andy
Mexico                           Kevin

当名称相等时，我的游标查询尝试合并区域名称

OPEN RegionCursor

FETCH NEXT
FROM RegionCursor
INTO @regionNext
    ,@NameNext

SET @name = @NameNext;

WHILE @@FETCH_STATUS = 0
BEGIN
    IF @NameNext != @name
    BEGIN
        INSERT @RegionTable
        SELECT @region
            ,@name

        SELECT @region = @regionNext
            ,@name = @NameNext
    END
    ELSE
        SET @region = COALESCE(@region + ', ', SPACE(0)) + @regionNext;

    FETCH NEXT
    FROM RegionCursor
    INTO @regionNext
        ,@NameNext
END

INSERT @RegionTable
SELECT @region
    ,@name

CLOSE RegionCursor;

DEALLOCATE RegionCursor;

然而，当这是运行时，它 return 是没有合并任何内容的原始数据集。我应该如何将查询修改为 return 所需的数据集？

Answer 1

您可以使用 CTE，它可能更干净一些：

;WITH CTE AS
( SELECT Region,
         Name,
         rn = ROW_NUMBER() OVER (PARTITION BY Name ORDER BY Name)
  FROM Table
)
SELECT c1.Region + ',' + c2.Region,
       c1.Name
FROM CTE c1
INNER JOIN CTE c2 ON c2.rn = c1.rn + 1

Answer 2

你不需要光标使用 XML PATH 技巧来做到这一点。

SELECT Name,
       LEFT(cs.Region, Len(cs.Region) - 1) AS Region                           
FROM   Yourtable a
       CROSS APPLY (SELECT Region + ','
                    FROM   Yourtable B
                    WHERE  a.name = b.name
                    FOR XML PATH('')) cs (Region)
GROUP  BY Name,
          LEFT(cs.Region, Len(cs.Region) - 1)

FIDDLE DEMO

SQL 服务器合并数据集

SQL Server Coalesce data set

sql

sql-server

coalesce