SQL查询问题

发布时间：2020-12-12 16:25:30 所属栏目：MsSql教程来源：网络整理

导读：假设我有两张桌子,“花园”和“鲜花”.这些桌子之间有1：n关系,因为在花园里可以有很多花.是否可以编写一个SQL查询,该查询返回具有以下结构的结果： GardenName Flower1Name Flower2Name .... (as long as there are entries in flowers)myGarden rose tulip

假设我有两张桌子,“花园”和“鲜花”.这些桌子之间有1：n关系,因为在花园里可以有很多花.是否可以编写一个SQL查询,该查询返回具有以下结构的结果：

GardenName     Flower1Name      Flower2Name .... (as long as there are entries in flowers)
myGarden        rose             tulip

解决方法

CREATE TABLE #Garden (Id INT,Name VARCHAR(20))
INSERT INTO #Garden
SELECT 1,'myGarden' UNION ALL
SELECT 2,'yourGarden'

CREATE TABLE #Flowers (GardenId INT,Flower VARCHAR(20))
INSERT INTO #Flowers
SELECT  1,'rose'  UNION ALL
SELECT  1,'tulip'  UNION ALL
SELECT  2,'thistle' 

DECLARE @ColList nvarchar(max)

SELECT @ColList = ISNULL(@ColList + ',','') + QUOTENAME('Flower' + CAST(ROW_NUMBER() OVER (ORDER BY (SELECT 0)) AS VARCHAR))
FROM #Flowers WHERE GardenId = (
SELECT TOP 1 GardenId
FROM #Flowers
ORDER BY COUNT(*) OVER (PARTITION BY GardenId) DESC

)

EXEC (N'
;WITH cte As
(
SELECT *,''Flower'' + CAST(ROW_NUMBER() OVER (PARTITION BY GardenId ORDER BY (SELECT 0)) AS VARCHAR) RN
FROM #Flowers F
)
SELECT Name,' + @ColList + N'
FROM cte 
JOIN #Garden g ON g.Id = GardenId
PIVOT (MAX(Flower) FOR RN IN (' + @ColList + N')) Pvt')


DROP TABLE #Garden
DROP TABLE #Flowers

Name                 Flower1              Flower2
-------------------- -------------------- --------------------
myGarden             rose                 tulip
yourGarden           thistle              NULL

（编辑：李大同）

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