1.1 基本概念 数据库(DataBase) 保存有组织的数据库的容器(通常是一个文件或一组文件)。 表(Table) 某种特定数据类型的结构化清单。 模式(Schema) 关于数据库和表的布局及特性的信息。 列(Column) 表中的一个字段。所有表都是由一个或多个列组成的。 数据类
1.1 基本概念
数据库(DataBase)
保存有组织的数据库的容器(通常是一个文件或一组文件)。
表(Table)
某种特定数据类型的结构化清单。
模式(Schema)
关于数据库和表的布局及特性的信息。
列(Column)
表中的一个字段。所有表都是由一个或多个列组成的。
数据类型
所允许的数据库的类型。每个表都有相应的数据类型，它限制(或允许）该类中存储的数据。
行(Row)
表中的一个记录
主键
一列(或多列)，其值能够唯一标准表中的每一行
满足以下条件的任何列都可以作为主键:
1.2 关于SQLSQL 是一种专门用来与数据库沟通的语言。
SQL扩展
标准SQL由ANSI标准委员会管理，从而成为ANSI SQL。在ANSI SQL的基础上，所有主要的DBMS，美国空间，网站空间，香港服务器租用，在实现ANSI SQL的基础上都会有自己的扩展，例如：PL/SQL、Transact-SQL等。
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