Database
A database is a collection of data stored in a computer system.
# Relational database
A database that contains a series of related tables that can be connected via their relationship.
# Database Normalization
Normalization is a process of organizing data in a relational database. For example, creating tables and establishing relationships between those tables. It is applied to eliminate data redundancy, increase data integrity, and reduce complexity in a database.
# Primary key
An identifier that references a column in which each value is unique.
Characteristics:
- a primary key is used to ensure data in a specific column is unique.
- It uniquely identifies a record in a relational database table.
- Only one primary key is allowed in a table and
- It cannot contain null or blank values.
# Composite key
A primary key constructed using multiple columns of a table.
# Foreign key
A field within a table that is a primary key in another table.
Characteristics:
- a column or group of columns in a relational database table that provides a link between the data and two tables.
- It refers to the field in a table that’s the primary key of another table.
- More than one foreign key is allowed to exist in a table.