这里有新鲜出炉的SQL Server教程,程序狗速度看过来!
SQL是英文Structured Query Language的缩写,意思为结构化查询语言。SQL语言的主要功能就是同各种数据库建立联系,进行沟通。按照ANSI(美国国家标准协会)的规定,SQL被作为关系型数据库管理系统的标准语言。
SQL Server 即 Microsoft SQL Server 。
这篇文章主要介绍了SQL Server 实现数字辅助表的相关资料,并附实例代码,需要的朋友可以参考下
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:
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 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
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 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:
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)
来源: http://www.phperz.com/article/17/0908/339239.html