SQLserver中的常量与变量、判断循环语句
数据库中的变量与常量 数据库中定义变量 【起临时存储数据的作用】 --- 数据库中定义变量 ( 运行时要从头到尾进行运行,从定义变量开始到赋值 ) -- 前面必须加 declare -- 定义变量 : declare @ 变量名 数据类型 declare @aa varchar ( 20 ) -- 赋值 set@aa
数据库中的变量与常量
数据库中定义变量
【起临时存储数据的作用】
---数据库中定义变量(运行时要从头到尾进行运行,从定义变量开始到赋值)
--前面必须加 declare
--定义变量 : declare @变量名 数据类型
declare @aa varchar(20)
--赋值 set @aa='你好'
set @aa ='武松'
select * from xuesheng where 姓名=@aa

--也可以在select后进行赋值
select @aa=姓名 from xuesheng where 学号=10

变量的应用如:

系统常量
--返回sqlserver自上次启动以来的连接数,不管成功还是失败
print @@connections
--返回执行上一个sql语句时的错误,返回代表没错,除了之外的是代表有错
print @@error
--返回当前使用的语言
print @@language
--受上一句影响的行数(在执行修改操作时,查看修改了多少行)
print @@rowcount
--返回安装数据库的版本信息
print @@version
判断、循环语句
【在数据库的判断循环语句使用中,没有大括号的使用,用begin end 代替,代码块写在begin end之间】
如:

If语句基本格式

While语句基本格式

例题,累加求和

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