SQL Server 基础 03 查询数据基础

 1 create table stu_info
 2 (
 3   sno int not null
 4   ,sname varchar(20) not null
 5   ,sex  varchar(2) not null
 6   ,birth  varchar(20) not null
 7   ,email  varchar(20) not null
 8   ,telephone int not null
 9   ,depart  varchar(20) not null
10 )
11 
12  
13  select distinct depart from dbo.stu_info
14  -- select order by depart from dbo.stu_info
15  --select sname ,datediff(year,birth,getdate()) from dbo.stu_info
16  --命名
17  select sname as 姓名 from dbo.stu_info
18  -- 把查询结果保存为一个新表
19  
20   select sname as 姓名 into sname2 from dbo.stu_info
21   -- 查询 sname2  即使用了 into后
22   select *  from sname2
23   --链接表字段
24    select sname+depart as 姓名来源 from dbo.stu_info

 1  --     where 
 2   select * from dbo.stu_info where sno>3
 3     select * from dbo.stu_info where sno=3
 4     select sno,sname,sex,depart from dbo.stu_info where sname>‘李四‘
 5 --  查询日期数据 SQL 默认格式 月/日/年
 6   select sno,birth as 生日,date  from dbo.stu_info where date>‘01/05/1980‘
 7    select sno,birth as 生日,date  from dbo.stu_info where date<‘01/05/1980‘ and date>‘01/05/1790‘
 8 --  按范围查询数据
 9  select * from dbo.stu_info where sno between 2 and 4
10   select * from dbo.stu_info where email is not null
11   
12   --排序查询数据 order by 后接 按哪个字段排名
13   select sno,sname,birth from dbo.stu_info order by sname
14   
15   -- 设置排名方向 asc 升 desc 降
16   select sno,sname,birth from dbo.stu_info order by sname desc
17   -- 按多列排序  在desc 后加上需要排序的字段 即可 （升序）
18   --........
19   -- 按字段位置排序 有时表达式过长，这样减少错误率 , 下面的2 代表select后面字段的第二个值
20   select sname ,datediff(year,date,getdate()) as 年龄 from dbo.stu_info order by 2 desc
21    
22    -- 查询前 几（2）行数据 关键字 top
23    select top 2 sno,sname,birth from stu_info order by birth
24    -- 查询前 n）行数据 关键字 top percent   百分之n
25    select top 2 percent sno,sname,birth from stu_info order by birth
26    
27     -- where 与 order by 结合使用 where 一定在前
28     select sno,sname,telephone,depart from stu_info where telephone is not null order by sno desc
29     
30