Basic operation of database on terminal

  Catalog

One 、 Database login operation

Two 、 Database operation statement

（1） Check how many databases the current server has

（2） Create database

（3） View database creation information     

 （4） Using a database

 （5） Delete database

3、 ... and 、 Operation of data table  

（1） Check how many tables there are in the selected database  

 （2） Look at the structure of a table

（3） Common data types

 （4） Create data table

（5） Delete table  

 （6） After the table is created, the attribute is modified

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One 、 Database login operation

When both the client and server are local

mysql -u root -p

When using a remote server , Use the complete login command

mysql -h  Server's IP Address -p  Port number  root( user name )  -p

Two 、 Database operation statement

（1） Check how many databases the current server has

show databases;

（2） Create database

create database  Database name ; 

 

create database if not exists  Database name ; 

Judge whether the current database already exists , If it exists, it will not be created

（3） View database creation information

show create database  Database name ;

Modify the coding of the existing database

alter database  Database name character set  Code name ; 

 （4） Using a database

All data tables are in a database , Therefore, the database must be selected before operation , The data table is Mysql The basic unit for data organization , A database is a folder

use  Database name ;

  Check the current database

select database();

 （5） Delete database

The default storage of the database is C:\ProgramData\MySQL\MySQL Server 5.7\Data

Deleting a database is a very dangerous operation , It's better not to , Be careful "[]" What is inside is optional , The back ones are all the same

drop [if exists]  Database name

 

3、 ... and 、 Operation of data table  

The data table is Mysql The basic unit for organizing data

（1） Check how many tables there are in the selected database  

show tables;

At this time, no element has been added to the table , So it shows empty

 

 *.frm The file saves the structure of the data table （ Table properties , Attribute type, etc ）

*.ibd The file saves the specific data and index information in the table

Pay attention to mysql8.0 Later versions will *.frm The files are merged into *ibd In file

 （2） Look at the structure of a table

desc  Data table name ;

 Field Is the property name

Type Is the property type

Null Whether yes is empty

Key It's the index

Default Is the default value

（3） Common data types

value type

  String type

varchar(10) Indicates that this data can be stored at most 10 Characters , The number of characters occupied in specific storage shall be subject to the stored data

char(10)  Indicates when this data is stored , No matter how many characters are stored , All in accordance with 10 Character storage

The date type

Time stamp ： Current time distance 1970 year 1 month 1 Japan 0 branch 0 The difference between seconds , Returns a long integer

datetime When inserting data, it will detect whether the format conforms to the date format ,'2022-06-03 20:05:10';

If the inserted data is only year month day , At this time, the hours, minutes and seconds are the default 0

If the inserted data has only hours, minutes and seconds , At this time, insert

 （4） Create data table

cteate table  Table name (

      The attribute name 1  Attribute types  comment' Field description ',

      The attribute name 2  Attribute types  comment' Field description ',

       .......,

      The attribute name n  Attribute types  comment' Field description '

);

View comment information

show create table  Table name

（5） Delete table  

drop table [if exists]  Table name ;

Deleting a table is as dangerous as deleting a database

 （6） After the table is created, the attribute is modified

alter table  Table name add  New attribute name   Attribute types ;

Delete a column

alter table  Table name drop  Column name ;

Modify a column , Data already exists in this column

alter table  Table name change  Original field name   new field name   type [ constraint ];

  Modify the name of the table

alter table  The old name of the table rename  The new name of the table ;

Modify the character set encoding of the table

alter table Table name convert to character set  New character set ;