數(shù)字輔助表是一個(gè)連續(xù)整數(shù)的數(shù)列，通常用來實(shí)現(xiàn)多種不同的查詢?nèi)蝿?wù)。大多分兩類：足夠大物理數(shù)字表和表函數(shù)，前者可以稱為靜態(tài)的，后者可以稱為動(dòng)態(tài)且按需生產(chǎn)。
物理數(shù)字表
物理數(shù)字表通常存在一個(gè)物理表，表記錄相對(duì)足夠大，相關(guān)的T-SQL代碼如下：
IF OBJECT_ID(N'dbo.Nums', 'U') IS NOT NULLBEGIN DROP TABLE dbo.Nums;ENDGO CREATE TABLE dbo.Nums ( Num INT NOT NULL, CONSTRAINT PK_U_CL_Nums_Num PRIMARY KEY CLUSTERED ( Num ASC ) );GO INSERT INTO dbo.Nums (Num)SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS RowNumFROM master.dbo.spt_values;GO
注意：如何填充物理數(shù)字表的方法很多，為了演示作用使用了一種。
測(cè)試的T-SQL代碼如下：
1 SELECT Num2 FROM dbo.Nums;3 GO
執(zhí)行后的查詢結(jié)果如下：
表函數(shù)
表函數(shù)實(shí)現(xiàn)使用交叉連接和CTE，SQL Server 2005和以上版本的T-SQL代碼如下：
IF OBJECT_ID(N'dbo.ufn_GetNums', N'IF') IS NOT NULLBEGIN DROP TABLE dbo.ufn_GetNums;ENDGO --==================================-- 功能: 獲取指定范圍的數(shù)字?jǐn)?shù)列-- 說明: 交叉最后層級(jí)的CTE得到的數(shù)據(jù)行：在L級(jí)（從0開始計(jì)數(shù)）得到的行的總數(shù)為2^2^L。-- 例如：在5級(jí)就會(huì)得到4 294 967 596行。5級(jí)的CTE提供了超過40億的行。-- 作者: XXX-- 創(chuàng)建: yyyy-MM-dd-- 修改: yyyy-MM-dd XXX 修改內(nèi)容描述--==================================CREATE FUNCTION dbo.ufn_GetNums( @bintLow BIGINT, @bintHigh BIGINT) RETURNS TABLEASRETURN WITH L0 AS (SELECT c FROM (VALUES(1), (1)) AS LO(c)), L1 AS (SELECT 1 AS c FROM L0 AS T CROSS JOIN L0 AS T2), L2 AS (SELECT 1 AS c FROM L1 AS T CROSS JOIN L1 AS T2), L3 AS (SELECT 1 AS c FROM L2 AS T CROSS JOIN L2 AS T2), L4 AS (SELECT 1 AS c FROM L3 AS T CROSS JOIN L3 AS T2), L5 AS (SELECT 1 AS c FROM L4 AS T CROSS JOIN L4 AS T2), Nums AS (SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS RowNum FROM L5) SELECT TOP (@bintHigh - @bintLow + 1) @bintLow + RowNum - 1 AS Num FROM Nums ORDER BY RowNum ASC;GO
SQL Server 2012增加了有關(guān)分頁的新特性，相關(guān)的T-SQL代碼如下:
IF OBJECT_ID(N'dbo.ufn_GetNums2', N'IF') IS NOT NULLBEGIN DROP TABLE dbo.ufn_GetNums2;ENDGO --==================================-- 功能: 獲取指定范圍的數(shù)字?jǐn)?shù)列-- 說明: 交叉最后層級(jí)的CTE得到的數(shù)據(jù)行：在L級(jí)（從0開始計(jì)數(shù)）得到的行的總數(shù)為2^2^L。-- 例如：在5級(jí)就會(huì)得到4 294 967 596行。5級(jí)的CTE提供了超過40億的行。 -- 作者: XXX-- 創(chuàng)建: yyyy-MM-dd-- 修改: yyyy-MM-dd XXX 修改內(nèi)容描述--==================================CREATE FUNCTION dbo.ufn_GetNums2( @bintLow BIGINT, @bintHigh BIGINT) RETURNS TABLEASRETURN WITH L0 AS (SELECT c FROM (VALUES(1), (1)) AS LO(c)), L1 AS (SELECT 1 AS c FROM L0 AS T CROSS JOIN L0 AS T2), L2 AS (SELECT 1 AS c FROM L1 AS T CROSS JOIN L1 AS T2), L3 AS (SELECT 1 AS c FROM L2 AS T CROSS JOIN L2 AS T2), L4 AS (SELECT 1 AS c FROM L3 AS T CROSS JOIN L3 AS T2), L5 AS (SELECT 1 AS c FROM L4 AS T CROSS JOIN L4 AS T2), Nums AS (SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS RowNum FROM L5) SELECT @bintLow + RowNum - 1 AS Num FROM Nums ORDER BY RowNum ASC OFFSET 0 ROWS FETCH FIRST @bintHigh - @bintLow + 1 ROWS ONLY;GO
以函數(shù)ufn_GetNums為例，演示相關(guān)的效果。獲取指定范圍的數(shù)字序列的T-SQL代碼如下：
SELECT NumFROM dbo.ufn_GetNums(11, 20);GO
執(zhí)行后的查詢結(jié)果如下：
博友如有其他更好的解決方案，也請(qǐng)不吝賜教，萬分感謝。
參考清單列表
1、《Microsoft SQL Server 2012 High-Performance T-SQL Using Window Functions》 作者 Itzik Ben-Gan（美國）（SQL Server Inside 有關(guān)書籍的作者）
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