Basic operations and basic data types of MySQL database

Catalog

1. Operation of database

（1） Inquire about , Show

（2） establish

（3） Delete database

（4） Use

2. Common data types

（1）. value type

（2）. String type

（3）. The date type

3. The operation of the table

（1）. View table structure

（2）. Create table

（3）. Delete table

4. summary

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1. Operation of database

（1） Inquire about , Show

show databases;

（2） establish

- Create directly （ If the database already exists , Report errors ）

create database Database name character set utf8mb4;（ Pay attention to setting the coding format when creating the database , Prevent Chinese miscoding ）

- If not created （if Database does not exist establish ）

create database if not exists Database name character set utf8mb4;

（3） Delete database

- Direct deletion （ If it doesn't exist, report it wrong ）：

drop database Database name ;

- If you have talent, delete it

drop database if exists Database name ;

（4） Use

（ appear No database selected error , Enter first / Using a database , To operate on the table ）

use Database name ;

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2. Common data types

（1）. The number class type

1. BIT Generally used to express java Inside boolean type
2. DECIMAL Inside M Indicates the specified length , Including integer and decimal places

（2）. String type

1. VARCHAR The corresponding is us java Used in String String of type
2. TEXT Used to store, for example, an article 、 Blog 、 Long text data such as websites

（3）. The date type

1. If your time is to include a time zone , To use TIMESTAMP

Java Inside Date and Timestamp Use

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3. The operation of the table

（1）. View table structure

grammar ：

desc Table name

（2）. Create table

grammar ：

CREATE TABLE table_name (

        field1 datatype,

        field2 datatype,

        field3 datatype

);

Be careful ：

        0. Naming rules exam_result, such All lowercase underline delimited naming format

        1. Ahead field Is the field name , The following is the data type of the field

        2. At the end of each field is a ” , ” separate , however There is no comma after the last field

        3. The last brace should end with a semicolon

        4. have access to comment Add field description . similar java Notes inside , Be careful comment Put before comma

        5. Syntax error may be caused by Chinese symbols Caused by the  

（3）. Delete table

grammar ：

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

eg:

4. summary

Show tables： View all tables

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