在SQL server中定义变量
create table stduser(
    id int,
    name varchar,
    age int,
    gender varchar
);

insert into stduser(id,name,age,gender)  values(1, ‘唐玄宗‘,125,‘man‘);
insert into stduser(id,name,age,gender)  values(2, ‘李高宗‘,453,‘woman‘);
insert into stduser(id,name,age,gender)  values(3, ‘唐太宗‘,412,‘man‘);
insert into stduser(id,name,age,gender)  values(4, ‘宋高宗‘,652,‘man‘);
insert into stduser(id,name,age,gender)  values(5, ‘慈溪‘,534,‘man‘);
insert into stduser(id,name,age,gender)  values(6, ‘贾宝玉‘,234,‘man‘);
insert into stduser(id,name,age,gender)  values(7, ‘林黛玉‘,564,‘woman‘);
insert into stduser(id,name,age,gender)  values(8, ‘薛宝钗‘,143,‘man‘);
insert into stduser(id,name,age,gender)  values(9, ‘王羲之‘,112,‘woman‘);
insert into stduser(id,name,age,gender)  values(10,‘吴广‘,129,‘woman‘);
insert into stduser(id,name,age,gender)  values(11,‘韩非‘,123,‘man‘);
insert into stduser(id,name,age,gender)  values(12,‘荀子‘,121,‘man‘);
insert into stduser(id,name,age,gender)  values(13,‘孟子‘,120,‘man‘);
insert into stduser(id,name,age,gender)  values(14,‘老子‘,122,‘man‘);
insert into stduser(id,name,age,gender)  values(15,‘卫庄‘,125,‘man‘);
insert into stduser(id,name,age,gender)  values(16,‘农夫山泉‘,128,‘man‘);
       
select * from stduser where gender=‘woman‘ order by age asc;

--定义变量 使用关键字declare
declare @num int;

--变量赋值的两种方式
--1 使用select 给变量赋值，将从表中查出来的值赋给变量，变量类型和表中对应的字段类型必须可以进行转换。
select @num = age from stduser where id=1;
print(@num);
select @num = 11;
print(@num);
--2 使用set 给变量赋值
set @num = 10;
print(@num);