[MySQL learning 08]

Data creation 、 Modify and delete

1.1 A procedure for storing data

1.2 Identifier naming rules

1.3 The basic types of data

The commonly used data types are described as follows ：

Create and manage databases

1. Create database


2. Management database

modify the database

Be careful ：

Delete database

Method 2: delete the database if it exists , If it doesn't exist, it will end silently .

The code problem

View the default encoding format ：show variables like “%char%”;

But it's still Chinese garbled

Operations on tables

There are two ways to create tables

Mode one ：


1. Use varchar To define a string , Must be in use varchar Indicate its length when .
2. If the character set is not specified when creating the table , The character set of the database where the table is located is used by default .

Mode two ：
Based on existing tables .


1. Copy table （ Include table data ）.
create table The new name of the table as select * from Table name already exists .
2. Copy table （ Excluding table data ）.
create table The new name of the table as select * from Table name already exists
where 1=2;（ Add a condition to filter ）.

Modify table

Add a field

Basic grammar ：alter table Table name add…;

The last two methods in the figure can adjust the field position .

Modify a field

Basic grammar ：alter table Table name modify…;

among aaa Is the default value .

Rename a field

Basic grammar ：alter table Table name change…; The old name comes first , New name after .

Delete a field

Basic grammar ：alter table Table name drop column…;

rename table , Delete table , Clear the table

1. rename table


2. Delete table


3. Clear the table
Clear table data only , The structure of the watch is still

DCL in commit and rollback

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