plsql中dbms元数据_DBMS中的元数据–概述和类型

plsql中dbms元数据

Metadata in DBMS is the data (details/schema) of any other data. It can also be defined as data about data. The word ‘Meta’ is the prefix that is generally the technical term for self-referential. In other words, we can say that Metadata is the summarized data for the contextual data.

DBMS中的元数据是任何其他数据的数据(详细信息/模式)。也可以将其定义为关于数据的数据。 “ Meta”一词是前缀，通常是自我指称的技术术语。换句话说，我们可以说元数据是上下文数据的汇总数据。

For example, consider the index of any book or novel; it serves as the metadata that leads us to the detailed data inside the book.

例如，考虑任何书籍或小说的索引；它用作元数据，可将我们引到书中的详细数据。

什么是元数据？ (What is Metadata?)

For instance, Metadata in DBMS has the following definitions:

例如，DBMS中的元数据具有以下定义：

Metadata is the value that leads us to the actual data;
元数据是将我们引向实际数据的价值；
The Metadata is an acronym for the detailed data;
元数据是详细数据的首字母缩写。
Metadata is the index of a library in the data warehouse;
元数据是数据仓库中库的索引；
Metadata is a description or schema of the actual data
元数据是实际数据的描述或架构

In a database, information is organized and stored in a structure. This data is arranged in tabular form (rows and columns) so that it can be accessed and reorganized quickly. After the structural arrangement of data, each part has its metadata as an index number in a book for each chapter. This index number is known as the metadata that defines the schema for other data.

在数据库中，信息被组织并存储在结构中。此数据以表格形式(行和列)排列，以便可以快速访问和重组。在对数据进行结构化排列之后，每个部分的元数据都作为书中每个章节的索引号。该索引号称为元数据，它定义其他数据的架构。

元数据的类型 (Types of Metadata)

There are several types of metadata according to their uses and domain.

根据元数据的用途和域，有几种类型的元数据。

Technical Metadata

技术元数据

This type of metadata defines database system names, tables names, table size, data types, values, and attributes. Further technical metadata also includes some constraints such as foreign key, primary key, and indices.

这种类型的元数据定义数据库系统名称，表名称，表大小，数据类型，值和属性。其他技术元数据还包括一些约束，例如外键，主键和索引。

Business Metadata

业务元数据

It consists of the ownership of data, changing policies, business rules and regulations, and other business details. This type of metadata is related to a particular business.

它由数据所有权，更改的策略，业务规则和法规以及其他业务详细信息组成。这种类型的元数据与特定业务有关。

Operational Metadata

操作元数据

This type includes the data which is currently under any operation. Besides, it represents the data that is used by executive-level managers to perform any task. Also, this type of metadata can be purged, archived, or activated and can also be migrated.

此类型包括当前正在执行任何操作的数据。此外，它代表执行级经理用于执行任何任务的数据。同样，可以清除，存档或**这种类型的元数据，也可以迁移它们。

Descriptive Metadata

描述性元数据

Descriptive metadata describes any file, folder, book, image, or video. It may include details of data such as title, author, date, size, author name, published on, and similarly others.

描述性元数据描述任何文件，文件夹，书本，图像或视频。它可能包含数据的详细信息，例如标题，作者，日期，大小，作者姓名，发表日期以及类似的内容。

DBMS中的元数据 (Metadata in DBMS)

Metadata in DBMS refers to the information that describes the schema and other information related to the stored data in the database, including storage, programs, data elements, usage, and additional related information. Let’s check the following types of metadata in DBMS.

DBMS中的元数据是指描述架构的信息以及与数据库中存储的数据相关的其他信息，包括存储，程序，数据元素，用法和其他相关信息。让我们检查一下DBMS中以下类型的元数据。

Schema

架构图

Tables
桌子
Columns
列
Constraints
约束条件
Indexes
指标
Sequences
顺序

Physical Execution

身体执行

Backup files
备份文件
Partitions
分区
Restored files
恢复的文件

Storage

存储

Table size
工作台尺寸
Datatype size
数据类型大小
Variable size
大小可变
Program size
程序大小
Number of rows and columns
行数和列数

Also, Metadata has a significant role in the database. Besides, it acts as a directory in the database for accessing the different files. Further, metadata can also be useful in many ways, like database reporting, auditing, querying, and transforming. It plays a crucial role in DBMS.

同样，元数据在数据库中也起着重要作用。此外，它还充当数据库中用于访问不同文件的目录。此外，元数据还可以在许多方面有用，例如数据库报告，审计，查询和转换。它在DBMS中起着至关重要的作用。

Metadata is also essential for interpreting the contents in the database. For example, a set of data with their schema, such as dates and names will get you confused. It becomes hard to identify the data you are interpreting. Besides, if there’s metadata for that existing data, you get an idea of the database you are interpreting with.

元数据对于解释数据库中的内容也至关重要。例如，一组带有其架构的数据(例如日期和名称)会让您感到困惑。识别要解释的数据变得很困难。此外，如果存在用于现有数据的元数据，那么您将了解要使用的数据库。

Basic metadata including rows and columns names that helps a user to easily identify the data being described. And if there’s a list of data with no metadata, it could be hard to say what the data is about. Now suppose, there’s a column with name ‘Expired domains’ will let you know that these domains have been expired. Additionally, if there’s another column of ‘Date’, it will let you know the date when it got expired.

包括行和列名称的基本元数据可帮助用户轻松识别所描述的数据。而且，如果存在没有元数据的数据列表，那么可能很难说出数据的含义。现在，假设有一列名为“ Expired domains”的字段将使您知道这些域已过期。此外，如果还有另一列“日期”，它将通知您过期的日期。

DBMS中的元数据示例 (An Example of Metadata in DBMS)

As you can see in the above image, a relational database stores the data as well as metadata in a structured way. The data stored in a structured way is called the Data Dictionary or System Catalog. The above metadata holds the following information:

如上图所示，关系数据库以结构化的方式存储数据和元数据。以结构化方式存储的数据称为数据字典或系统目录。上面的元数据包含以下信息：

Tables (rows and columns)
表(行和列)
Datatypes
资料类型
Values
价值观
Table relationships
表关系
Constraints
约束条件
and others
和别的

Further, through this information, it’s easier to access or identify any database.

此外，通过此信息，可以更轻松地访问或标识任何数据库。

关于元数据的总结 (Final Words on Metadata)

Metadata is data about the data and not the actual context of data. Hence, it can be made publically available as it only describes the raw data and doesn’t provide any access to it. Metadata gives the idea and summary details about any database which is enough to understand what the file is but does not give the complete instance of that file.

元数据是有关数据的数据，而不是数据的实际上下文。因此，可以公开使用它，因为它仅描述原始数据，不提供对原始数据的任何访问。元数据提供了有关任何数据库的概念和摘要详细信息，这些信息足以了解文件是什么，但没有提供该文件的完整实例。

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翻译自: https://www.thecrazyprogrammer.com/2019/12/metadata-in-dbms.html