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In relational databases, the information schema (information_schema) is an ANSI-standard set of read-only views that provide information about all of the tables, views, columns, and procedures in a database. [1]
Visual schema/E-R design: the ability to draw entity-relationship diagrams for the database. If missing, the following two features will also be missing; Reverse engineering - the ability to produce an ER diagram from a database, complete with foreign key relationships
Views can represent a subset of the data contained in a table. Consequently, a view can limit the degree of exposure of the underlying tables to the outer world: a given user may have permission to query the view, while denied access to the rest of the base table. [2] Views can join and simplify multiple tables into a single virtual table. [2]
Conversely, PostgreSQL has applied more of the specification implementing cross-table, cross-schema, and then left room for future cross-database functionality. MySQL aliases schema with database behind the scenes, such that CREATE SCHEMA and CREATE DATABASE are analogs. It can therefore be said that MySQL has implemented cross-database ...
They are not to be confused with a database schema—the abstract, structural, organizational specification which defines how every table's data relates to data within other tables. All PostgreSQL database objects, except for a few global objects such as roles and tablespaces, exist within a schema. They cannot be nested, schemas cannot contain ...
The term "schema" refers to the organization of data as a blueprint of how the database is constructed (divided into database tables in the case of relational databases). The formal definition of a database schema is a set of formulas (sentences) called integrity constraints imposed on a database.
That is the domain of the physical schema. Now logical schemas describe data in terms of relational tables and columns, object-oriented classes, and XML tags. A single set of tables, for example, can be implemented in numerous ways, up to and including an architecture where table rows are maintained on computers in different countries.
The three schema approach. [3] The three-schema approach in software engineering is an approach to building information systems and systems information management, that promotes the conceptual model as the key to achieving data integration. [4] A schema is a model, usually depicted by a diagram and