Types of Database and components.

Relational Model.

Every administrator must learn to base their models on this described one, so that they can have updated the information that is exposed in the related tables.

1. The first attribute of a table will become a primary key.

2. The following two attributes that will be the foreign keys are selected.

3. The others will be attributes.

Cardinality They are the lines that interlace a primary key with foreign keys. They are classified in:

1. One to one: can only be related to another element of another entity.

2. From one to many: is when one element of an entity is related to several of another.

3. From many to many: is when two or more elements of an entity are related in the same way to another entity.

4. From one to zero or many: is when an element of a table is related to many or none.

5. Many to zero or many: is when many elements of a table are related to many or none.

UML standard.