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:

  IF OBJECT_ID(N'dbo.Nums', 'U') IS NOT NULL  BEGIN    DROP TABLE dbo.Nums;  END  GO     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 RowNum  FROM master.dbo.spt_values;  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:

SQL Server 实现数字辅助表实例代码

 表函数

    表函数实现使用交叉连接和CTE, Server 2005和以上版本的T-SQL代码如下:

  IF OBJECT_ID(N'dbo.ufn_GetNums', N'IF') IS NOT NULL  BEGIN    DROP TABLE dbo.ufn_GetNums;  END  GO     --==================================  -- 功能: 获取指定范围的数字数列  -- 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。  --    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。  -- 作者: XXX  -- 创建: yyyy-MM-dd  -- 修改: yyyy-MM-dd XXX 修改内容描述  --==================================  CREATE FUNCTION dbo.ufn_GetNums  (    @bintLow BIGINT,    @bintHigh BIGINT  ) RETURNS TABLE  AS  RETURN     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

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

  IF OBJECT_ID(N'dbo.ufn_GetNums2', N'IF') IS NOT NULL  BEGIN    DROP TABLE dbo.ufn_GetNums2;  END  GO     --==================================  -- 功能: 获取指定范围的数字数列  -- 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。  --    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。   -- 作者: XXX  -- 创建: yyyy-MM-dd  -- 修改: yyyy-MM-dd XXX 修改内容描述  --==================================  CREATE FUNCTION dbo.ufn_GetNums2  (    @bintLow BIGINT,    @bintHigh BIGINT  ) RETURNS TABLE  AS  RETURN     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:

SQL Server 实现数字辅助表实例代码
 

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 Server 2012 High-Performance T-SQL Using Functions》 作者 Itzik Ben-Gan(美国)(SQL Server Inside 有关书籍的作者)

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