SQL 编程技巧

Ø  简介

本文主要介绍编写 SQL 时的一些编程技巧，方便有时候忘了便于查看，主要包含以下内容：

1.   SQL 语句中使用 +=、-=、*=、/= 运算符

2.   值为 NULL 的列或局部变量，参与计算的结果始终为 NULL

3.   将一个数值四舍五入至指定小数位

4.   删除重复记录，并保留一条记录

5.   使用 ROW_NUMBER() 生成序号并排序（支持多个排序字段）

1.   SQL 语句中使用 +=、-=、*=、/= 运算符

DECLARE 秒）插入的记录。

5.   使用 ROW_NUMBER() 生成序号并排序（支持多个排序字段）

WITH ce1 (Id1, Id2, Name) AS (

SELECT 3 AS Id1, 8 AS Id2, 'A' AS Name UNION

SELECT 2 AS Id1, 7 AS Id2, 'B' AS Name UNION

SELECT 4 AS Id1, 6 AS Id2, 'C' AS Name UNION

SELECT 2 AS Id1, 5 AS Id2, 'D' AS Name UNION

SELECT 3 AS Id1, 4 AS Id2, 'E' AS Name UNION

SELECT 4 AS Id1, 3 AS Id2, 'F' AS Name UNION

SELECT 3 AS Id1, 2 AS Id2, 'G' AS Name UNION

SELECT 4 AS Id1, 1 AS Id2, 'H' AS Name

) SELECT * FROM (SELECT ROW_NUMBER() OVER(ORDER BY Id1 ASC, Id2 DESC) AS RowNo, * FROM ce1) AS T

--ORDER BY T.RowNo ASC  --有时可能排序不正确，可以再通过 RowNo 排序