SQL查询问题

Question

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

Answer 1

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

Answer 2

看看在SQL Server中使用Pivot.这是一个很好的链接,了解它的工作原理:

http://www.kodyaz.com/articles/t-sql-pivot-tables-in-sql-server-tutorial-with-examples.aspx

好吧,我想我已经开始工作了.试试这个:

with temp as
(
    select 'myGarden' as name, 'test1' as flower
    union
    select 'myGarden','test2'
    union
    select 'myGarden','test5'
    union
    select 'abeGarden','test4'
    union
    select 'abeGarden','test5'
    union 
    select 'martinGarden', 'test2'
)

select* from temp
pivot
(
  max(flower)
  for flower in (test1,test2,test3,test4,test5)
) PivotTable

您还可以使in子句中的值动态化.由于这是一个CTE,我不能在我的例子中.