MySQL beginner benefits

1、 Database related operations

1.1、 Display database

Code :show database;

show and databases There is a space between , It can be multiple , But don't omit in addition SQL Case insensitive

Examples of operation :

1.2、 Create database

Format :create database Database name ;

The name of the database can be used casually But it can't be SQL Keywords in If you really want to use Just enclose it in reverse quotation marks The counter quotation marks are in Esc below Tab above

Examples of operation :

1.3、 Select database

Format :use Database name ;

Before proceeding further with the database , You need to select the database first , Do it again

Example operation :

1.4、 Delete database

Format :drop database Database name :

Delete the database Use with caution !!! “ Delete library from , To run ”

Code example :

1.5、 stay cmd Run in MySQL

Input :mysql -u root -p password
Code example ;

Try entering the above command :
show database;
create database Database name ;
use Database name ;
drop database Database name :
Code example :

2、 Data sheet

There can be many data tables in a database
Each data table can have many rows , Each line becomes a " Record "
Each row can have many columns , Each column is called a " Field "
MySQL Such a database The columns in each row are consistent
Suppose the first row has three columns So each row has three columns

2.1、 Create table

Select the database to be operated before operation
use student;

When specifying columns , List first , Type after Format :create table Table name ( Name type , Name type …);

Code example :

When the library name to be operated is not specified could not be built

Code example :

2.2、 See the table

Format :show tables;
The above selected database ;
Code example :

Code :show tables;
Running results :
±------------------+
| Tables_in_student |
±------------------+
| student |
±------------------+
1 row in set (0.00 sec)

2.3、 View table structure

See how many columns there are in a table , What type is each column , What is the name of each column and other supplementary information for each column

grid

type :desc Table name ; desc<===>describe— describe

Code example :

Field----> Field Null among :
Yes Indicates that this column is allowed to be empty
No Indicates that this column cannot be empty
Default—> The default value is
In the middle of Null The delegate field is empty by default
Extra–> Additional information

2.4、 practice

There is a store data , Record customers and shopping , It consists of the following three tables :
goods goods( Product id goods_id, Trade name goods_name, The unit price unitprice, Commodity categories category, for
Ying Shang provider)
Customer customer( Customer number customer_id, full name name, address address, mailbox email, Gender sex, Id card
card_id)
Buy purchase( Purchase order No order_id, Customer number customer_id, Commodity number goods_id, Purchase quantity nums)

Process description :

Create database

Select database

Create database tables

goods

Customer

Buy

Examples of operation :