SQL server(一)變量的定義

在SQL server中定義變量
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, '賈寶玉',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, '薛寶釵',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,'吳廣',129,'woman');
insert into stduser(id,name,age,gender)  values(11,'韓非',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,'衛庄',125,'man');
insert into stduser(id,name,age,gender)  values(16,'農夫山泉',128,'man');
       
select * from stduser where gender='woman' order by age asc;

--定義變量 使用關鍵字declare
declare @num int;

--變量賦值的兩種方式
--1 使用select 給變量賦值，將從表中查出來的值賦給變量，變量類型和表中對應的字段類型必須可以進行轉換。
select @num = age from stduser where id=1;
print(@num);
select @num = 11;
print(@num);
--2 使用set 給變量賦值
set @num = 10;
print(@num);