Database Concepts - A Short Post about the Relational Database Model

via Wikipedia

Relational Database Model:
The relational database model, different from the entity relation model, shows specific data and information about a database table. A relational database model contains two parts: An instance, and a Schema.

Schema:
The schema is specific name of the relation, or the name of each column. If you think back to the Entity-Relationship Diagrams, there are names that have relationships to each other, these names would be the part of the schema. In the above picture, the schema would be the part that says "login", "first", and "last."

Instance:
The instance are the rows of data that pairs with the schema. In the above picture, the instance would be the rows of names.

Relations:
As you can see from the image above, the specific row of information for "Mark" is linked to another table that contains the specific key's phone number. This, is what the Entity Relationship Diagram has drawn out; the connection between one login key to a foreign key.

Usage:
With the Relational Database, we can use query language to query for data. Although our queries can be efficient, the DBMS is mostly responsible for making queries efficient.