你的位置:首页 > 数据库

[数据库]SQL Server数字辅助表的实现


    数字辅助表是一个连续整数的数列,通常用来实现多种不同的查询任务。大多分两类:足够大物理数字表和表函数,前者可以称为静态的,后者可以称为动态且按需生产。
物理数字表
    物理数字表通常存在一个物理表,表记录相对足够大,相关的T-SQL代码如下:
 1 IF OBJECT_ID(N'dbo.Nums', 'U') IS NOT NULL 2 BEGIN 3   DROP TABLE dbo.Nums; 4 END 5 GO 6  7 CREATE TABLE dbo.Nums  8 ( 9   Num INT NOT NULL,10   CONSTRAINT PK_U_CL_Nums_Num PRIMARY KEY CLUSTERED11   (12     Num ASC13   ) 14 );15 GO16 17 INSERT INTO dbo.Nums (Num)18 SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS RowNum19 FROM master.dbo.spt_values;20 GO

注意:如何填充物理数字表的方法很多,为了演示作用使用了一种。


测试的T-SQL代码如下:
1 SELECT Num2 FROM dbo.Nums;3 GO

执行后的查询结果如下:




 
表函数
    表函数实现使用交叉连接和CTE,SQL Server 2005和以上版本的T-SQL代码如下:
 1 IF OBJECT_ID(N'dbo.ufn_GetNums', N'IF') IS NOT NULL 2 BEGIN 3   DROP TABLE dbo.ufn_GetNums; 4 END 5 GO 6  7 --================================== 8 -- 功能: 获取指定范围的数字数列 9 -- 说明: 交叉最后层级的CTE得到的数据行:在L级(从0开始计数)得到的行的总数为2^2^L。10 --    例如:在5级就会得到4 294 967 596行。5级的CTE提供了超过40亿的行。11 -- 作者: XXX12 -- 创建: yyyy-MM-dd13 -- 修改: yyyy-MM-dd XXX 修改内容描述14 --==================================15 CREATE FUNCTION dbo.ufn_GetNums16 (17   @bintLow BIGINT,18   @bintHigh BIGINT19 ) RETURNS TABLE20 AS21 RETURN 22   WITH23     L0 AS (SELECT c FROM (VALUES(1), (1)) AS LO(c)),24     L1 AS (SELECT 1 AS c FROM L0 AS T CROSS JOIN L0 AS T2),25     L2 AS (SELECT 1 AS c FROM L1 AS T CROSS JOIN L1 AS T2),26     L3 AS (SELECT 1 AS c FROM L2 AS T CROSS JOIN L2 AS T2),27     L4 AS (SELECT 1 AS c FROM L3 AS T CROSS JOIN L3 AS T2),28     L5 AS (SELECT 1 AS c FROM L4 AS T CROSS JOIN L4 AS T2),29     Nums AS (SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS RowNum FROM L5)30 31   SELECT TOP (@bintHigh - @bintLow + 1) @bintLow + RowNum - 1 AS Num32   FROM Nums33   ORDER BY RowNum ASC;34 GO

    SQL Server 2012增加了有关分页的新特性,相关的T-SQL代码如下:


 1 IF OBJECT_ID(N'dbo.ufn_GetNums2', N'IF') IS NOT NULL 2 BEGIN 3   DROP TABLE dbo.ufn_GetNums2; 4 END 5 GO 6  7 --================================== 8 -- 功能: 获取指定范围的数字数列 9 -- 说明: 交叉最后层级的CTE得到的数据行:在L级(从0开始计数)得到的行的总数为2^2^L。10 --    例如:在5级就会得到4 294 967 596行。5级的CTE提供了超过40亿的行。 11 -- 作者: XXX12 -- 创建: yyyy-MM-dd13 -- 修改: yyyy-MM-dd XXX 修改内容描述14 --==================================15 CREATE FUNCTION dbo.ufn_GetNums216 (17   @bintLow BIGINT,18   @bintHigh BIGINT19 ) RETURNS TABLE20 AS21 RETURN 22   WITH23     L0 AS (SELECT c FROM (VALUES(1), (1)) AS LO(c)),24     L1 AS (SELECT 1 AS c FROM L0 AS T CROSS JOIN L0 AS T2),25     L2 AS (SELECT 1 AS c FROM L1 AS T CROSS JOIN L1 AS T2),26     L3 AS (SELECT 1 AS c FROM L2 AS T CROSS JOIN L2 AS T2),27     L4 AS (SELECT 1 AS c FROM L3 AS T CROSS JOIN L3 AS T2),28     L5 AS (SELECT 1 AS c FROM L4 AS T CROSS JOIN L4 AS T2),29     Nums AS (SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS RowNum FROM L5)30 31   SELECT @bintLow + RowNum - 1 AS Num32   FROM Nums33   ORDER BY RowNum ASC34   OFFSET 0 ROWS FETCH FIRST @bintHigh - @bintLow + 1 ROWS ONLY;35 GO36 

以函数ufn_GetNums为例,演示相关的效果。获取指定范围的数字序列的T-SQL代码如下:


SELECT NumFROM dbo.ufn_GetNums(11, 20);GO

执行后的查询结果如下:



 
博友如有其他更好的解决方案,也请不吝赐教,万分感谢。
 
参考清单列表
1、《Microsoft SQL Server 2012 High-Performance T-SQL Using Window Functions》 作者 Itzik Ben-Gan(美国)(SQL Server Inside 有关书籍的作者)