Database Database Basics

1.1 Database Overview

in short, a database is a warehouse where data is stored. To facilitate the storage and management of data, data is stored on disk in a specific pattern. Through the database management system, the data stored in the database can be effectively organized and managed. Today, there are many excellent databases such as Oracle, SQL Server, MySQL, and so on. 1.2. Database generics database generics are the rules that a database should follow. Database generics are also called paradigms. The four most common paradigms currently used in relational databases are:First Paradigm (1NF)second paradigm (2NF)Third paradigm (3NF)BCN Paradigm (BCNF) when designing a database, the paradigm of minimum requirements that a database needs to meet is the first paradigm. The requirements table for the first paradigm cannot have duplicate fields, and each field can no longer be split. If there is a database even if the first paradigm is not satisfied, it can not be called a relational database. It is possible to create tables in this relational database only if the requirements of the first paradigm are met. On the basis of satisfying the first paradigm, the database can be refined in one step. Refinement can make the database meet the requirements of the second paradigm. The third paradigm and the BCN paradigm can be obtained by thinning in turn. 1.3 Database System1.3.1 Database SystemMany people think that database is the database system, or DBS, for short. In fact, the scope of the database system is much larger than the database. Database system is not a simple database, but is composed of database, database management system and application development tools. Many times, database administrators and users can be part of a database system.  a database is where data is stored. a database Management system, or DBMS, is the software used to define data, manage, and maintain data. It is an important part of the database system. Application systems are software that requires the use of a database. For example, student management system is an application system, this application system needs the database to manage its data. Application development tools are used to develop application systems.  1.3.2 SQL Languagethe full name of the SQL (Structured query Language) language is the Structured Query language. The database management system manages the data in the database through the SQL language.  The SQL language consists of three parts:Data Definition language (Language, referred to as DDL)Data Manipulation language (manipulation Language, referred to as DML)Data Control Language (Language, referred to as DCL)data Query Language (Language, referred to as DQL) 1.3.3 Database access Technologyapplication, the program language needs to use database access technology to access the database. SQL statements embedded in a program only work if you use database access techniques. Different program languages are not the same way to access a database.  JDBC is a Java API for executing SQL statements. Multiple relational databases can be accessed through JDBC. JDBC consists of a set of classes and interfaces written in the Java language. When using JDBC, you must install the driver connector/j.  PHP provides programmers with the MySQL function module, PHP5 later to provide mysqli interface. PHP can access MySQL database via MySQL function module and mysqli interface.  

Database Database Basics