T-SQL如何分组两个字段并连接另一个

Question

我正在尝试对 2 个字段进行分组并返回第三个字段，该字段是前 2 个共有的另一个字段的值与给定 ProductID 的串联。这是我的数据：

ProductID   Currency   Price   Territory
1           USD        6.99    US
1           EUR        4.99    GR
1           EUR        4.99    HU
1           EUR        4.99    LT
2           USD        7.99    US
2           EUR        5.99    GR
2           EUR        5.99    HU

我希望结果返回如下：

ProductID   Currency   Price   Territories
1           USD        6.99    US
1           EUR        6.99    GR, HU, LT

我可以提取 Currenty 和 Price 列，但不能连接它们共有的 Territories：

SELECT Currency, Price
FROM TerritoryPricing
WHERE ProductID = 1
GROUP BY Currency, Price

如何连接地区？

Answer 1

你可以使用 Concat：

SELECT ProductID, Currency, Price, CONCAT(Territory)
GROUP BY territory
FROM employee_tbl;

或者创建一个类似这样的 colace 函数

CREATE FUNCTION [dbo].[terr]
(
    @territoryID int
)
RETURNS varchar(max)
AS
BEGIN
    declare @output varchar(max)
    select @output = COALESCE(@output + ', ', '') + territory
    from TerritoryPricing
    where territoryid = @territoryID

    return @output
END

GO

SELECT UserID, [dbo].terr(territoryID)
FROM TerritoryPricing
GROUP BY territory

GO

Answer 2

测试这段代码

DECLARE @S VARCHAR(8000)
SELECT 
    Currency, 
    Price , 
    Territories = (Select @S = @S  + Territory FROM TerritoryPricing as T2 WHERE T1.Currency = T2.Currency AND T1.Price = T2.Price) ,
    Empty = (select @S ='') 
FROM TerritoryPricing as T1
WHERE ProductID = 1
GROUP BY Currency, Price

Answer 3

您可以使用 SQL 的 XML 处理来生成具有 SQL 2000 及更高版本的连接列表：

create table #TerritoryPricing ( ProductID int, Currency varchar(3), Price decimal(10,2), Territory varchar(2))
insert into #TerritoryPricing values (1,'USD',6.99,'US')
insert into #TerritoryPricing values (1,'EUR',4.99,'GR')
insert into #TerritoryPricing values (1,'EUR',4.99,'HU')
insert into #TerritoryPricing values (1,'EUR',4.99,'LT')
insert into #TerritoryPricing values (2,'USD',7.99,'US')
insert into #TerritoryPricing values (2,'EUR',5.99,'GR')
insert into #TerritoryPricing values (2,'EUR',5.99,'HU')

SELECT Currency, Price,
    SUBSTRING(
        (SELECT ( ',' + ltrim(rtrim(Territory)))  
        FROM #TerritoryPricing t2
        WHERE t1.Currency = t2.Currency  
            and t1.Price = t2.Price
            and ProductID = 1
        ORDER BY t2.Territory
        FOR XML PATH('')
        ), 2, 8000) Territories
FROM #TerritoryPricing t1
WHERE ProductID = 1
GROUP BY Currency, Price