默认全局变量是两个@@开头, 可用show variables查看所有默认变量:

@@user

#declare定义变量只能用在储存过程中

#declare 变量名 数据类型 可选类型

declare num int；

declare age int defalut 100;

#定义全局变量， 可以用 set声明:

#@变量名

#有两种写法, @name := value / @name = value

set @age=18;

set @age:=18;

select @name:=user();

select @name=user();

mysql> select @a=password from mysql.user$

+-------------+

| @a=password |

+-------------+

|           1 |

|           1 |

|           1 |

+-------------+

3 rows in set (0.00 sec)

mysql> select @a:=password from mysql.user$

+-------------------------------------------+

| @a:=password                              |

+-------------------------------------------+

| *81F5E21E35407D884A6CD4A731AEBFB6AF209E1B |

| *81F5E21E35407D884A6CD4A731AEBFB6AF209E1B |

| *81F5E21E35407D884A6CD4A731AEBFB6AF209E1B |

+-------------------------------------------+

#:=与=赋值时区别从上面可以看到

#:=显示结果， = 不会显示结果

#其实用:=/= 赋值都一样

create procedure cc1111()

    begin

      declare gan char;

      set gan = user();

      select gan;

    end$