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This article will explain in detail what DDL means in MySQL. The editor thinks it is very practical, so I share it with you as a reference. I hope you can get something after reading this article.

DDL in MySQL represents database definition statements, which are used to create tables, indexes, views, stored procedures, triggers, and so on.

The commonly used sentence keywords are: CREATE,ALTER,DROP,TRUNCATE,COMMENT,RENAME.

The schema described by DDL must be compiled by computer software and converted into a format that is convenient for computer storage, query and manipulation. The program that completes this conversion work is called the schema compiler.

The schema compiler processes schema definitions to produce two main types of data: data dictionaries and data types and structure definitions.

The data dictionary and the internal structure information of the database are the basis for creating the database corresponding to the schema, and the corresponding logical structure of each database is created according to this information; the access and query of the database data also determines the way and type of data access according to the schema information, as well as the relationship between the data and the integrity constraints on the data.

The data dictionary is the internal information representation of the schema, and the data dictionary is stored differently for different DBMS.

The definition of data type and structure means that when the application connects to the database, the application needs to understand the data type and structure generated and extracted. It is the definition of the data type and structure of the user workspace provided for various host languages, which makes the logical structure of the user workspace consistent with the database and reduces the process of data conversion. The definition of this data type and structure is usually implemented by a header file.

There are usually two ways to define database schemas: interactively defining schemas and describing text schemas through data description language DDL.

Database level

Show all databases: show databases

Access to a database: use db_name

Create a database: create databse db_name

Create a database of the specified character set: create database db_name character set utf8

Display database creation information: show create database db_name

Modify the database encoding: alter database db_name character set gb2312

Delete a database: drop database db_name

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