[MySQL] database and table operations

[MySQL] database and table operations

1. Database operations

Enter the database

mysql -u root -p

1.1 Display the current database

SHOW DATABASES;

1.2 Create a database

Grammar rules

CREATE DATABASE [IF NOT EXISTS] db_name [create_specification [,create_specification] ...]
描述信息
create_specification:
 [DEFAULT] CHARACTER SET charset_name
 [DEFAULT] COLLATE collation_name

Description: The
uppercase keyword
[] is optional.
CHARACTER SET: Specify the character set used by the database.
COLLATE: Specify the character set of the database.
Example:
Create a database named goods

CREATE DATABASE goods;

Note: When we create a database without specifying the character set and verification rules, the system uses the default character set: utf8, the verification rule is: utf8_ general_ ci
If the system does not have a database of goods, then create a database called goods, if If not

CREATE DATABASE IF NOT EXISTS goods;

If the system does not have a database of goods, create a goods database that uses the utf8mb4 character set, if not, do not create it (know it, generally generated by default)

CREATE DATABASE IF NOT EXISTS db_test CHARACTER SET utf8mb4;

1.3 Delete the database

grammar

DROP DATABASE [IF EXISTS] db_name;

Note: After the database is deleted, the corresponding database cannot be seen inside, and all the tables and data inside are deleted

1.4 Using the database

grammar:

use 数据库名;

2. Operation of the table

When you need to operate a table in the database, you need to use the
common data types of the database :
INT: integer
DECIMAL (M, D): floating point type
VARCHAR (SIZE): string type
TIMESTAMP: date type
text: long text data

2.1 Create a data table

grammar

CREATE TABLE table_name (
 field1 datatype,
 field2 datatype,
 field3 datatype
);

You can use the commentadditional field description
Example:
Add a student information table in the students library

create table stu(
id int,
name varchar(20) comment '姓名',
sex verchar(8),
birthday timestamp
);

2.2 View form information

Statement:

desc + ‘表名’;

2.3 Delete Table

grammar

DROP TABLE[IF EXISTS] tbl_name [, tbl_name] ...

Example:
– Delete the stu_test table

drop table stu_test;

– If the stu_test table exists, delete the stu_test table

drop table if exists stu_test