A3.2.3 Outline the different data types used in relational databases

Common relational database data types can be grouped into:
- string data types
- numeric data types
- date/time data types

String data types

CHAR
- fixed length
- the length is defined explicitly, for example CHAR(7)
- if the inserted value is shorter, spaces may be used to pad it
- suitable for fixed-length values such as:
  - IDs
  - passwords
  - country codes
  - status flags
VARCHAR
- variable length
- suitable for:
  - names
  - emails
  - descriptions
TEXT
- used for longer text such as:
  - blog posts
  - articles
  - comments
  - product reviews
MEDIUMTEXT
- used for larger text such as:
  - long documentation
  - large JSON data
  - novels or books
LONGTEXT
- used for extremely large text such as:
  - large archives
  - very large documentation
  - full codebases
ENUM
- one value must be chosen from a predefined list
- suitable for:
  - status fields
  - user roles
  - categories with exactly one allowed choice
SET
- zero or more values can be chosen from a predefined list
- suitable for:
  - user interests
  - multiple skills
  - multiple tags or categories

BIT
- stores bit-field values where each bit is 0 or 1
- suitable for:
  - boolean values
  - on/off states
  - permission flags
BOOL / BOOLEAN
- stores true/false style values
- suitable for:
  - toggle settings
  - status indicators
INT
- stores whole numbers
- suitable for:
  - primary keys
  - foreign keys
  - counts
  - quantities
FLOAT
- stores approximate decimal numbers
- suitable when exact precision is less important
DECIMAL(a,b)
- stores exact decimal numbers with fixed precision
- a is the total number of digits
- b is the number of digits after the decimal point
- suitable for:
  - money
  - measured values where exact precision matters