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An entity–relationship model (or ER model) describes interrelated things of interest in a specific domain of knowledge. A basic ER model is composed of entity types (which classify the things of interest) and specifies relationships that can exist between entities (instances of those entity types).
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
An entity–relationship model (ERM) is an abstract conceptual representation of structured data. Entity–relationship modeling is a relational schema database modeling method, used in software engineering to produce a type of conceptual data model (or semantic data model ) of a system, often a relational database , and its requirements in a ...
Attributes in ER diagrams are usually modeled as an oval with the name of the attribute, linked to the entity or relationship that contains the attribute. ER models are commonly used in information system design; for example, they are used to describe information requirements and / or the types of information to be stored in the database during ...
The database schema is the structure of a database described in a formal language supported typically by a relational database management system (RDBMS). 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 enhanced entity–relationship (EER) model (or extended entity–relationship model) in computer science is a high-level or conceptual data model incorporating extensions to the original entity–relationship (ER) model, used in the design of databases.
Snowflake schema used by example query. The example schema shown to the right is a snowflaked version of the star schema example provided in the star schema article. The following example query is the snowflake schema equivalent of the star schema example code which returns the total number of television units sold by brand and by country for 1997.
An EXPRESS-G diagram for Family schema A simple EXPRESS data model looks like fig 2, and the code like this: SCHEMA Family; ENTITY Person ABSTRACT SUPERTYPE OF (ONEOF (Male, Female)); name: STRING; mother: OPTIONAL Female; father: OPTIONAL Male; END_ENTITY; ENTITY Female SUBTYPE OF (Person); END_ENTITY; ENTITY Male SUBTYPE of (Person); END ...