MySQL Base (DDL)

SQL classification

SQL statements can be divided into 3 categories
DDL: Data definition language, defining data segments, databases, data tables, and other DML: data manipulation statements for adding, deleting, updating, and querying database records DCL: Data control statements, statements that control the level of permission and access to different data segments directly

to get started, start MySQL service net start MySQL, go to MySQL, mysql-u root-p (U back with database user,-p indicates need to enter password)

     
1. DDL statements

The language in which objects inside the database are created, deleted, modified, and so on.

1.1 Creating a DatabaseCREATE database----;        

After creating the database, view the database show databases;

                

Select the database you want to manipulate use---
View the tables in the database show tables;

                           1.2 Deleting a database

drop database----;

1.3 Creating a Table

CREATE TABLE---(name1 type constraint, name2 type constraint ...);
Look at the table you just created to see if it meets the requirements desc--;

1.4 Deleting a table

drop table----;

1.5 Modifying a table

To modify the data type of an item in a table ALTER TABLE---modify---;

           

Add new field ALTER TABLE---add colum----;

         

delete field ALTER TABLE---drop colum---;
Modify the field name ALTER TABLE---change---;

MySQL Base (DDL)