What is the abbreviation for Data Definition Language?

The abbreviation of data definition language is "DDL", and the full English name is "Data Definition Language". It is a language used to describe real-world entities to be stored in the database. These definitions include structure definitions and operation method definitions. wait.

The abbreviation of Data Definition Language is "DDL".

Database schema definition language DDL (Data Definition Language) is a language used to describe real-world entities to be stored in the database.

Introduction

These definitions include structure definitions, operation method definitions, etc.

The database schema definition language is not a programming language. The DDL database schema definition language is a component of the SQL language (Structured Query Language). The SQL language includes statements from four major programming language categories: data definition language (DDL), data manipulation language (DML), data control language (DCL), and transaction control language (TCL).

The implementation of rewriting query statements mainly involves rewriting two major types of statements in the SQL language, namely data definition language DDL and data manipulation language DML.

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 is called a schema compiler.

The schema compiler processes schema definitions and mainly produces two types of data: data dictionaries and data type and structure definitions.

The data dictionary and the internal structure information of the database are the basis for creating the database corresponding to the mode. Based on this information, the logical structure corresponding to each database is created; the access and query of the database data also determine the data storage based on the mode information. The method and type of retrieval, as well as the relationship between data and the integrity constraints on the data.

The data dictionary is the internal information representation of the schema. The storage method of the data dictionary varies for different DBMS.

The definition of data types and structures means that when an application program connects to a database, the application program needs to understand the data types and structures generated and extracted. It is the data type and structure definition of the user workspace provided for various host languages, making the logical structure of the user workspace and the database consistent, reducing the data conversion process. The definition of this data type and structure is usually used in a header file. accomplish.

There are usually two ways to define a database schema: interactively defining the schema and defining the schema through data description language DDL description text.

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