Скачать или смотреть Components of DBMS

A database management system (DBMS) is software for creating, storing, maintaining, and accessing database files. A DBMS makes using databases more efficient. A database engine, the heart of DBMS software, is responsible for data storage, manipulation, and retrieval. It converts logical requests from users into their physical equivalents (e.g., reports) by interacting with other components of the DBMS (usually the data manipulation component).

The data definition component is used to create and maintain the data dictionary and define the structure of files in a database. Any changes to a database’s structure, such as adding a field, deleting a field, changing a field’s size, or changing the data type stored in a field, are made with this component.

The data manipulation component is used to add, delete, modify, and retrieve records from a database. Typically, a query language is used for this component. Structured Query Language (SQL) is a standard fourth-generation query language used by many DBMS packages, such as Oracle Database 12c and Microsoft SQL Server. SQL consists of several keywords specifying actions to take.

With query by example (QBE), you request data from a database by constructing a statement made up of query forms. With current graphical databases, you simply click to select query forms instead of having to remember keywords, as you do with SQL.

In large organizations, database design and management is handled by the database administrator (DBA). Although, with complex databases this task is sometimes handled by an entire department.