SQL Server 实现数字辅助表实例代码

数据库  /  管理员 发布于 5年前   162

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 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：

IF OBJECT_ID(N'dbo.ufn_GetNums', N'IF') IS NOT NULLBEGIN  DROP TABLE dbo.ufn_GetNums;ENDGO --==================================-- 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 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 NULLBEGIN  DROP TABLE dbo.ufn_GetNums2;ENDGO --==================================-- 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 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）

感谢阅读，希望能帮助到大家，谢谢大家对本站的支持！