Postgresql 中文操作指南
2.2. Concepts #
PostgreSQL 是 relational database management system (RDBMS)。这意味着它是一个系统,用于管理存储在 relations 中的数据。关系本质上是 table 的数学术语。如今,将数据存储在表中的概念是如此普遍,以至于它看起来似乎显而易见,但还有许多其他组织数据库的方法。类 Unix 操作系统上的文件和目录构成了层次数据库的一个示例。一个更现代的发展是面向对象数据库。
PostgreSQL is a relational database management system (RDBMS). That means it is a system for managing data stored in relations. Relation is essentially a mathematical term for table. The notion of storing data in tables is so commonplace today that it might seem inherently obvious, but there are a number of other ways of organizing databases. Files and directories on Unix-like operating systems form an example of a hierarchical database. A more modern development is the object-oriented database.
每个表都是 rows 的命名集合。给定表中的每行都有一组相同的命名 columns ,并且每列都是特定数据类型。虽然列在每行中都有固定的顺序,但务必要记住,SQL 绝不以任何方式保证表中行的顺序(尽管可以对它们进行显式排序以进行显示)。
Each table is a named collection of rows. Each row of a given table has the same set of named columns, and each column is of a specific data type. Whereas columns have a fixed order in each row, it is important to remember that SQL does not guarantee the order of the rows within the table in any way (although they can be explicitly sorted for display).
表被分组到数据库中,而由单个 PostgreSQL 服务器实例管理的一组数据库组成了一个数据库 cluster 。
Tables are grouped into databases, and a collection of databases managed by a single PostgreSQL server instance constitutes a database cluster.