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