Question

List the data types that are allowed for SQL attributes.

Short answer

The data types allowed for SQL attributes are numeric (INTEGER, SMALLINT, DECIMAL, NUMERIC, FLOAT, REAL, DOUBLE PRECISION), character (CHAR, CHAR VARYING, TEXT), boolean (BOOLEAN), date and time (DATE, TIME, TIMESTAMP), and binary types (BIT, BIT VARYING, BLOB).

Step-by-step solution

Numeric Types

These are the types used to store numeric data. They include INTEGER, SMALLINT, DECIMAL, NUMERIC, FLOAT, REAL, DOUBLE PRECISION.

Character Types

These types are used to store character strings. They include CHAR, CHAR VARYING, TEXT.

Boolean Type

This type is used to store boolean values. The type here is BOOLEAN.

Date and Time Types

These are used to store date and time values. The types include DATE, TIME, TIMESTAMP.

Binary Types

These are used to store binary data. They include BIT, BIT VARYING, BINARY LARGE OBJECT (BLOB).

Key concepts

Numeric Data Types

Numeric data types in SQL are crucial for handling numerical information. These data types allow you to store numbers ranging from whole numbers to floating point numbers.

Here are some popular numeric data types:

• INTEGER: Used for whole numbers without fractions.
• SMALLINT: Like INTEGER, but uses less storage space, ideal for smaller ranges.
• DECIMAL and NUMERIC: These types store exact numbers with a fixed number of decimal places.
• FLOAT, REAL, DOUBLE PRECISION: These represent approximate numbers, often used for large number ranges or scientific calculations.

Managing numeric data accurately is essential for computations and data analysis.

Character Data Types

Character data types are indispensable for storing text and string data in SQL. They are used widely for holding names, addresses, and any alphanumeric data that isn’t numerical.

The main character data types include:

• CHAR: Fixed-length character type, where the length must be specified and padded with spaces as needed.
• CHAR VARYING (VARCHAR): Variable-length strings that can resize to fit the input data up to a specified maximum length.
• TEXT: Used for variable-length strings of any size, great for large bodies of text.

These data types help in managing large text fields efficiently.

Boolean Data Types

Boolean data types are used in SQL to store truth values: true or false. This is particularly useful for conditional logic and flags within a database.

While SQL standards often include a BOOLEAN type, implementation of BOOLEAN can vary between different SQL databases. Generally, a BOOLEAN data type may internally be represented by using integers or bits in some systems, where:

• TRUE: Typically represented by a non-zero value, often 1.
• FALSE: Typically represented by 0.

Even though it is a simple data type, it plays a powerful role in filtering data and controlling processes.

Date and Time Data Types

Date and time data types are essential for managing temporal data in your SQL databases. They support storing dates, times, or combinations of the two.

The key date and time data types are:

• DATE: Used to store dates (year, month, day) without any time.
• TIME: Stores time (hour, minute, second) without any date information.
• TIMESTAMP: Captures both date and time in a single data type, down to fractional seconds.

These data types support various date and time formatting, making them extremely useful for timeline records and scheduling tasks.

Binary Data Types

Binary data types are used to store data in a binary format, supporting the storage of unstructured data like images, documents, and multimedia files.

Key binary data types include:

• BIT: A simple binary type used to store a fixed number of bits.
• BIT VARYING: Stores a variable number of bits up to a specified limit.
• BLOB (Binary Large Object): Designed for large amounts of binary data, often used to store large multimedia files.

Understanding binary data types is critical when your data requirements extend beyond traditional text and numbers.