我想此時(shí)不妨使用字符串參數(shù)來幫助我們解決這種情況，利用字符串分割的方法將一個(gè)參數(shù)分割成數(shù)個(gè)參數(shù)來解決。下面我們看一個(gè)例子：
假設(shè)現(xiàn)在給你一個(gè)產(chǎn)品信息列表（顯示出各個(gè)商品的基本信息），現(xiàn)在我想要根據(jù)所選擇商品進(jìn)行統(tǒng)計(jì)（任意選擇幾種），例如統(tǒng)計(jì)出價(jià)格10,11-20,21-30,31-40,41-50,50以上的商品個(gè)有多少個(gè)（姑且認(rèn)為就統(tǒng)計(jì)這些）。此時(shí)如果使用存儲過程就勢必需要傳入所選商品的id作為參數(shù)，但是id個(gè)數(shù)是不固定的。此時(shí)估計(jì)會有人這樣寫：
復(fù)制代碼 代碼如下:
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author: jianxin160
-- Create date: 2010.11.05
-- Description: 統(tǒng)計(jì)商品
-- =============================================
ALTER PROCEDURE StatProductInfo
(
@ids VARCHAR(8000)
)
AS
BEGIN
DECLARE @followingTen INT
DECLARE @elevenToTwenty INT
DECLARE @twentyOneToThirty INT
DECLARE @thirtyOneToFourty INT
DECLARE @fourtyOneToFifty INT
DECLARE @fiftyOrMore INT
SELECT @followingTen=COUNT(*)
FROM dbo.Products
WHERE ProductID IN(@ids) AND UnitPrice10
SELECT @elevenToTwenty=COUNT(*)
FROM dbo.Products
WHERE ProductID IN(@ids) AND UnitPrice BETWEEN 11 AND 20
SELECT @twentyOneToThirty=COUNT(*)
FROM dbo.Products
WHERE ProductID IN(@ids) AND UnitPrice BETWEEN 21 AND 30
SELECT @thirtyOneToFourty=COUNT(*)
FROM dbo.Products
WHERE ProductID IN(@ids) AND UnitPrice BETWEEN 31 AND 40
SELECT @fourtyOneToFifty=COUNT(*)
FROM dbo.Products
WHERE ProductID IN(@ids) AND UnitPrice BETWEEN 41 AND 50
SELECT @fiftyOrMore=COUNT(*)
FROM dbo.Products
WHERE ProductID IN(@ids) AND UnitPrice>50
SELECT @followingTen AS '$10',@elevenToTwenty AS '$11-$20',
@twentyOneToThirty AS '$21-$30',@thirtyOneToFourty AS '$31-$40',
@fourtyOneToFifty AS '$41-$50',@fiftyOrMore AS '>$50'
END
GO
其實(shí)如果你測試一下（例如：EXEC dbo . StatProductInfo '3,4,8,10,22' ）是有問題的，sql server認(rèn)為這整個(gè)是一個(gè)參數(shù)，轉(zhuǎn)換時(shí)出錯(cuò)。此時(shí)我們想一下如果這些字段在一個(gè)虛表中就容易操作多了，但是一般虛表是有其他表通過查詢得到，現(xiàn)在根本無法查詢又哪來的虛表呢？聰明的朋友或許已經(jīng)想到可以使用"表值函數(shù)"。對，答案就是使用"表值函數(shù)"。我們知道"表值函數(shù)"可以返回一個(gè)"Table"類型的變量（相當(dāng)于一張?zhí)摫?，存放于?nèi)存中），我們首先將字符串分割存放到"表值函數(shù)"的一個(gè)字段中，然后我們再從"表值函數(shù)"中查詢就可以了（這個(gè)例子也是"表值函數(shù)"的一個(gè)典型應(yīng)用）。具體sql如下：
復(fù)制代碼 代碼如下:
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author: cmj
-- Create date: 2010.11.05
-- Description: 返回一個(gè)Table,只有一列，每一行的數(shù)據(jù)就是分割好的字符串
-- =============================================
CREATE FUNCTION GetSplitFieldsByString
(
@toSplitString varchar(1000),
@splitChar varchar(10)
)
RETURNS
@tb TABLE(sp varchar(100))
AS
BEGIN
DECLARE @i INT
SET @toSplitString=RTRIM(LTRIM(@toSplitString))
SET @i=CHARINDEX(@splitChar,@toSplitString)
WHILE @i>0
BEGIN
INSERT @tb VALUES(LEFT(@toSplitString,@i-1))
SET @toSplitString=RIGHT(@toSplitString,LEN(@toSplitString)-@i)
SET @i=CHARINDEX(@splitChar,@toSplitString)
END
IF LEN(@toSplitString)>0
INSERT @tb VALUES(@toSplitString)
RETURN
END
GO
然后我們稍微修改一下存儲過程：
復(fù)制代碼 代碼如下:
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- =============================================
-- Author: jianxin160
-- Create date: 2010.11.05
-- Description: 統(tǒng)計(jì)商品
-- =============================================
ALTER PROCEDURE StatProductInfo
(
@ids VARCHAR(8000)
)
AS
BEGIN
DECLARE @followingTen INT
DECLARE @elevenToTwenty INT
DECLARE @twentyOneToThirty INT
DECLARE @thirtyOneToFourty INT
DECLARE @fourtyOneToFifty INT
DECLARE @fiftyOrMore INT
SELECT @followingTen=COUNT(*)
FROM dbo.Products
WHERE ProductID IN(SELECT sp FROM dbo.GetSplitFieldsByString(@ids,',')) AND UnitPrice10
SELECT @elevenToTwenty=COUNT(*)
FROM dbo.Products
WHERE ProductID IN(SELECT sp FROM dbo.GetSplitFieldsByString(@ids,',')) AND UnitPrice BETWEEN 11 AND 20
SELECT @twentyOneToThirty=COUNT(*)
FROM dbo.Products
WHERE ProductID IN(SELECT sp FROM dbo.GetSplitFieldsByString(@ids,',')) AND UnitPrice BETWEEN 21 AND 30
SELECT @thirtyOneToFourty=COUNT(*)
FROM dbo.Products
WHERE ProductID IN(SELECT sp FROM dbo.GetSplitFieldsByString(@ids,',')) AND UnitPrice BETWEEN 31 AND 40
SELECT @fourtyOneToFifty=COUNT(*)
FROM dbo.Products
WHERE ProductID IN(SELECT sp FROM dbo.GetSplitFieldsByString(@ids,',')) AND UnitPrice BETWEEN 41 AND 50
SELECT @fiftyOrMore=COUNT(*)
FROM dbo.Products
WHERE ProductID IN(SELECT sp FROM dbo.GetSplitFieldsByString(@ids,',')) AND UnitPrice>50
SELECT @followingTen AS '$10',@elevenToTwenty AS '$11-$20',@twentyOneToThirty AS '$21-$30',
@thirtyOneToFourty AS '$31-$40',@fourtyOneToFifty AS '$41-$50',@fiftyOrMore AS '>$50'
END
GO
這樣通過執(zhí)行EXEC dbo . StatProductInfo '3,4,8,10,22' 就可以得到想要的結(jié)果了：
試試這樣會不會快一些
復(fù)制代碼 代碼如下:
SELECT SUM(CASE WHEN UnitPrice 10 THEN 1 ELSE 0 END) '$10',
SUM(CASE WHEN UnitPrice BETWEEN 11 AND 20 THEN 1 ELSE 0 END) '$11-$20',
SUM(CASE WHEN UnitPrice BETWEEN 21 AND 30 THEN 1 ELSE 0 END) '$21-$30',
...
SUM(CASE WHEN UnitPrice > 50 THEN 1 ELSE 0 END) '>$10'
FROM dbo.Products
WHERE ProductID IN(SELECT sp FROM dbo.GetSplitFieldsByString(@ids,','))
