Data table operation of MySQL database (DDL data definition language)

1. Create a data table

Data table: a two-dimensional table, a table is composed of multiple columns, and each type in the table is called a field of the table

Student Information

stu_num char(8) not null	stu_name varchar(20) not null	this_gender char(2) not null	stu_age int not null	this_tel char(11) not null unique	this_qq varchar(11) unique

Take the above student information form as an example to create a form in the MySQL database, the statement is as follows (note: the corresponding database should be selected before creation):

create table students(
stu_num char(8) not null unique,
stu_name varchar(20) not null,
stu_gender char(2) not null,
stu_age int not null,
stu_tel char(11) not null unique,
stu_qq varchar(11) unique
);

2. Query data table

Query all tables in the current database:

show tables;

Query the specified table structure in the current database:

desc 表名字;

3. Delete the data table

## 删除数据表
drop table 数据表名;

## 当数据表存在时删除数据表
drop table if exists 数据表名;

Fourth, modify the data table and fields

## 修改表名
alter table 旧表名 rename to 新表名;

## 数据表也是有字符集的，默认字符集和数据库⼀致
alter table 表名 character set utf8;

## 添加列（字段）
alter table 表名 add 字段名 varchar(200);

## 修改列（字段）的列表和类型
alter table 表名 change 旧的字段名 新字段名 字段类型;

## 只修改列（字段）类型
alter table 表名 modify 字段名 新的字段类型;

## 删除列（字段）
alter table stus drop 字段名;