Databse

Seite 1

Data types:

Text

Alphanumeric

Boolean

Integer

Date/Time

Relationships:

One-to-one:

When each record in one table only connects to one record in another table. Each foreign key value will like to one primary key value and each primary key value will be linked to one foreign key value.

One-to-many:

When each record in one table can connect to many records in another table

Many-to-many:

Each record can connect to each other

Difference between a flat file and a relational database:

Flat file is database that has one table and no relationships. It is called flat because it has two dimensions fields and records.

Referential Integrity:

Only exists when data in the foreign key of the table on the many side of a relationship exists in the primary key of the table on the one side of a relationship.

Types of validation:

Lookup

Range

Presence

Length

Format

Normalization:

Starts with a flat file and ends up with a set of related tables.

0NF:

Contains non-atomic,repeated groups and redundant data.

1NF:

Must contain atomic data

No repeated groups of data

Must have unique key

2NF:

Remove dependent keys and these will eventually go into a separate table.

3NF:

No non key dependencies. No fields dependent of another field.

Data Dictionary:

A document that contains the structure of the data held inside of a database. Data about data.

Field names, Data Types, Field Size