Catalog

SQL Non technical quick start

Basic query

Query all columns

Query multiple columns

Query result de duplication

Query results limit the number of rows returned

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Conditions of the query

Sort multiple columns after searching

Find the student information of the school is Peking University

Look for ages greater than 24 Users of

Find user information for a certain age group

Find user information except Fudan University

use where Filter null exercises

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• SQL Non technical quick start

• Basic query

• Query all columns

  Code ：select sentence

select * from user_profile

• Query multiple columns

Code ： From table select Out ： equipment ID, Gender , Age school listing is OK

select  device_id,gender,age,university -- equipment ID, Gender , Age school 
from user_profile

• Query result de duplication

  Code ：distinct duplicate removal

select distinct university
FROM user_profile

• Query results limit the number of rows returned

  Code ：where Conditions of the query

select device_id 
from user_profile
where  id<=2

• Rename the queried column

Code ：as rename , Rename and ：

  select device_id as user_infos_example 
  from user_profile 
  where id<=2

• Conditions of the query

• Sort after finding

Code ：order by Name asc/desc   asc Ascending ,desc Descending , The default sort is Ascending

select device_id,age from user_profile order by age 

• Sort multiple columns after searching

Code ：

select device_id, gpa, age from user_profile
order by gpa asc, age asc

• Sort in descending order after finding

  Code ：desc Descending order

select device_id,gpa,age
from user_profile
order by gpa desc,age desc

• Find the student information of the school is Peking University

  Code ：where Statement condition query

select device_id,university
from user_profile
where university=' Peking University, '

• Look for ages greater than 24 Users of

  Code ：

select device_id,gender,age,university 
from user_profile 
where age>24

• Find user information for a certain age group

  Code ：and Parallel conditions

select device_id,gender,age
from user_profile
where age>=20 and age<=23

• Find user information except Fudan University

Code ：!=  It's not equal to

select device_id, gender, age, university
from user_profile
where university != ' Fudan University '

• use where Filter null exercises

  Code ：

select device_id,gender,age,university
from user_profile
where age !=' '

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