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HomeDatabaseMysql Tutorialsql server和mysql变量赋值的区别 以及 MySql Declare_MySQL

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sql server和mysql都是我们经常用到的数据库系统,下面就为您介绍sql server和mysql变量赋值的区别,希望对您能有所启迪。

sql server中变量要先申明后赋值:

局部变量用一个@标识,全局变量用两个@(常用的全局变量一般都是已经定义好的);

申明局部变量语法:declare @变量名 数据类型;例如:declare @num int;

赋值:有两种方法式(@num为变量名,value为值)

set @num=value;   或   select @num=value;

如果想获取查询语句中的一个字段值可以用select给变量赋值,如下:

select @num=字段名 from 表名 where ……

mysql变量赋值不用事前申明,在用的时候直接用“@变量名”使用就可以了。

第一种用法:set @num=1; 或set @num:=1; //这里要使用变量来保存数据,直接使用@num变量

第二种用法:select @num:=1; 或 select @num:=字段名 from 表名 where …… (张英:似乎mysql中不能使用 select @p1 := c1, @p2:=c2 from tb 方式赋值)

注意上面两种赋值符号,使用set时可以用“=”或“:=”,但是使用select时必须用“:=赋值”bitsCN.com
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