W-database Basics

The database system consists of three parts: Database (DB), database management system (DBMS), and database application system data plus are used to store data, which stores two types of data: user Data and System Data Dictionary, specifically for users in the system and user permissions, various statistical information and other databases are stored in the computer for a long time organized and shareable

The database system consists of three parts: Database (DB), database management system (DBMS), and database application system data plus are used to store data, which stores two types of data: user Data and System Data/Data Dictionary, specifically for users in the system and user permissions, various statistical information and other databases are stored in the computer for a long time organized and shareable

The database system consists of three parts: Database (DB), database management system (DBMS), and database application system

Data addition is used to store data. It stores two types of data: user data and System Data/Data Dictionary, specifically, the user and user permissions in the system, and various statistical information.

A database is a set of data that has been stored in a computer for a long time and can be shared.

Each DBMS supports a data model. Mainstream DBMS such as Oracle, Sybase, DB2, SQLServer, and MySQL support relational data models.

Basic functions of DBMS:

1. Data Definition

2. Data Operations

3. Database Operation Management

4. Database recommendations and maintenance functions

DBMS consists of two parts: Query processor and Storage Manager

Query processors include: Data Definition Language (DDL) compiler, Data Control Language (DML) compiler, embedded DML pre-compiler, query optimization, and other core programs.

The Storage Manager includes authorization and security control, integrity check manager, Transaction Manager, file manager, and buffer management.

Different models are also required for implementing database applications: Conceptual Models (also known as information models), logical models, and physical models.

The logical model is directly oriented to the logical structure of the database. There is usually a set of strictly defined, unambiguous syntax and semantics database languages that people can use to define, application programmers program data in databases based on logical models. Each DBMS supports a logical Model. The most important logical Model in a database is Hierarchical Model ), network Model, Rational Model, Object Oriented Model, and Object Rational Model)

Three elements of the data model: data structure, data operations, and data constraints