Home Database Mysql Tutorial SQLserver中的常量与变量、判断循环语句

SQLserver中的常量与变量、判断循环语句

Jun 07, 2016 pm 03:24 PM
sqlserver judgment variable constant cycle data statement

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

SQLserver中的常量与变量、判断循环语句

 

 --也可以在select后进行赋值

 select @aa=姓名 from xuesheng where 学号=10

SQLserver中的常量与变量、判断循环语句

 

变量的应用如:

SQLserver中的常量与变量、判断循环语句

 

 

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:

SQLserver中的常量与变量、判断循环语句

 

 

If语句基本格式

SQLserver中的常量与变量、判断循环语句

 

While语句基本格式

SQLserver中的常量与变量、判断循环语句

 

例题,累加求和

SQLserver中的常量与变量、判断循环语句

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