SQL理论课-Class 1

select name（一个或多个属性）

from instructor（一个或者多个表）

where dept_name = 'cs'（满足条件）

--去重复：

select distinct dept_name

from instructor

select distinct dept_name,id

from instructor

select distinct 主码

from 表

select salary*1.1

from instructor

找导师工资出来，输出结果为1.1倍原工资数据

select salary>8000 and dept_name = 'cs'

select salary*1.1 as over_salary

 from instructor

字符串1+字符串2 ：字符串拼接

upper(字符串)

lower(字符串)

-'Intro%' --寻找开头为Intro

-'%abc%'  --寻找中间含有abc

-'___'   --寻找三位长度

-'___%'  --寻找至少三位

select name

from instructor

where name like '%abc%' --注意用like进行筛讯

select name

from instructor

where salary between 9000 and 10000

select name, course_id

from instructor, teaches

where (instructor.ID, dept_name) = (teaches.ID, ’Biology’);

– Example: order by name desc

Can sort on multiple attributes

– Example: order by dept_name, name --按照两个元素排序，字符串首字母。