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 CLUSTERED
11     (
12         Num ASC
13     ) 
14 );
15 GO
16  
17 INSERT INTO dbo.Nums (Num)
18 SELECT ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS RowNum
19 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 Num
2 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: XXX
12 -- 创建: yyyy-MM-dd
13 -- 修改: yyyy-MM-dd XXX 修改内容描述
14 --==================================
15 CREATE FUNCTION dbo.ufn_GetNums
16 (
17     @bintLow BIGINT,
18     @bintHigh BIGINT
19 ) RETURNS TABLE
20 AS
21 RETURN 
22     WITH
23         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 Num
32     FROM Nums
33     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: XXX
12 -- 创建: yyyy-MM-dd
13 -- 修改: yyyy-MM-dd XXX 修改内容描述
14 --==================================
15 CREATE FUNCTION dbo.ufn_GetNums2
16 (
17     @bintLow BIGINT,
18     @bintHigh BIGINT
19 ) RETURNS TABLE
20 AS
21 RETURN 
22     WITH
23         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 Num
32     FROM Nums
33     ORDER BY RowNum ASC
34     OFFSET 0 ROWS FETCH FIRST @bintHigh - @bintLow + 1 ROWS ONLY;
35 GO
36  

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 Num
FROM 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)
posted @ 2015-12-27 21:02 剑走江湖 阅读(...) 评论(...) 编辑 收藏