SQL查詢問題

Question

讓我們說我有兩個表，「花園」和「花」。這些表格之間有1：n的關係，因爲在花園裏可以有很多花。是否可以編寫一個SQL查詢返回的結果結構如下：

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

動態SQL與遊標是我能想到的唯一途徑，而且也不會漂亮。

Answer 3

看看在SQL Server中使用Pivot。這裏是一個很好的鏈接，越過它是如何工作：

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

好吧，我想我得到它的工作。試試這個：

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 

你也可以將在in條款的動態值。由於這是一個CTE，我不能在我的例子中。

Answer 4

如果你只是想在這個時間會給你的數據，一個花園結果：

select gardenName from tblGarden where gardenid = 1 
Union ALL 
select tblFLowers.flowerName from tblFlowers where gardenid = 1