[Sql brush topic] Query information data--Day1

目录

前言

Query information data

Inquire about the students of the specified school

Find students of a specified age

Query students of a specified age group

Search for students at a given university

小结

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前言

数据库技术是通过研究数据库的结构、存储、设计、管理以及应用的基本理论和实现方法,并利用这些理论来实现对数据库中的数据进行处理、分析和理解的技术.即：数据库技术是研究、管理和应用数据库的一门软件科学.其中mysqlIt is a very hot database.

Query information data

Inquire about the students of the specified school

思路：We already know the information about the database,可以看到是存在5confidence,And there is little repetition of the same information.Then we can think,If we can try to specify the table name,Then specify the table name学校信息查询,然后输入指定的id这样就可以了,Then let's experiment.

题目描述：

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代码：

SELECT device_id,university
FROM user_profile
WHERE university="北京大学"

 结果

Find students of a specified age

思路：We already know the information about the database,可以看到是存在5confidence,And there is little repetition of the same information.Then we can think,If we can try to specify the table name,Then specify the table name年龄信息查询,然后输入指定的id这样就可以了,Then let's experiment.

题目描述：

代码：

SELECT device_id,gender,age,university
FROM user_profile
WHERE age>24;

 结果：

 

Query students of a specified age group

思路：We already know the information about the database,可以看到是存在5confidence,And there is little repetition of the same information.Then we can think,If we can try to specify the table name,Then specify the table name年龄范围查询,然后输入指定的id这样就可以了,Then let's experiment.

题目描述：

代码：

SELECT device_id,gender,age from user_profile where age between 20 and 23

结果：

Search for students at a given university

思路：We already know the information about the database,可以看到是存在5confidence,And there is little repetition of the same information.Then we can think,If we can try to specify the table name,Then specify the table nameRemove school enquiries,然后输入指定的id这样就可以了,Then let's experiment.

题目描述：

代码：

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

结果：

小结

Brushing questions is very helpful for us to familiarize ourselves with and consolidate the content of knowledge points.

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