What is a "database entity" and what types of DBMS items are considered entities? [closed]

Question

Is it things like tables? Or would it also include things like constraints, stored procedures, packages, etc.?

I've looked around the internet, but finding elementary answers to elementary questions is sometimes a little difficult.

Answer 1

That's quite a general question!

Basically, all types that the database system itself offers, like NUMERIC, VARCHAR etc., or that the programming language of choice offers (int, string etc.) would be considered "atomic" data(base) types.

Anything that you - based on your program's or business' requirements - build from that, business objects and so forth, are entities.

Tables, constraints and so forth are database-internal objects needed to store and retrieve data, but those are general not considered "entities". The data stored in your tables, when retrieved and converted into an object, that then is an entity.

Marc

Answer 2

In the entity relationship world an entity is something that may exist independently and so there is often a one-to-one relationship between entities and database tables. However, this mapping is an implementation decision: For example, an ER diagram may contain three entities: Triangle, Square and Circle and these could potentially be modelled as a single table: Shape.

Also note that some database tables may represent relationships between entities.

Answer 3

This seems helpful: http://en.wikipedia.org/wiki/Entity-relationship_model

In a database an entity is a table. The table represents whatever real world concept you are trying to model (person, transaction, event).

Contraints can represents relationships between entities. These would be foreign keys. They also enforce rules like first_name can not be blank (null). A transaction must have 1 or more items. An event must have a date time.

Stored Procedures / Packages / Triggers could handle more complex relationships and/or they can handle business rules, just depends on what it's doing.