SQL Data Types Reference Guide

Reference for common SQL data types across databases.

Numeric Types

Syntax:

INT | BIGINT | DECIMAL(p,s) | FLOAT | DOUBLE

Store integer and decimal numbers.

Example:

CREATE TABLE products (id INT, price DECIMAL(10,2), weight FLOAT);

💡 Note: DECIMAL for exact precision (money), FLOAT for approximate

String Types

Syntax:

CHAR(n) | VARCHAR(n) | TEXT | NVARCHAR(n)

Store text data. CHAR is fixed-length, VARCHAR is variable.

Example:

CREATE TABLE users (country_code CHAR(2), name VARCHAR(100), bio TEXT);

💡 Note: NVARCHAR for Unicode support

Date/Time Types

Syntax:

DATE | TIME | DATETIME | TIMESTAMP | TIMESTAMPTZ

Store dates and times.

Example:

CREATE TABLE events (event_date DATE, start_time TIME, created_at TIMESTAMP);

💡 Note: TIMESTAMPTZ includes timezone (PostgreSQL)

Boolean

Syntax:

BOOLEAN | BIT

Store true/false values.

Example:

CREATE TABLE users (is_active BOOLEAN DEFAULT true);

💡 Note: SQL Server uses BIT, others use BOOLEAN

JSON Types

Syntax:

JSON | JSONB

Store JSON documents. JSONB is binary and indexable.

Example:

CREATE TABLE logs (data JSONB);

💡 Note: JSONB preferred for querying (PostgreSQL)

UUID

Syntax:

UUID | UNIQUEIDENTIFIER

Store universally unique identifiers.

Example:

CREATE TABLE users (id UUID PRIMARY KEY DEFAULT gen_random_uuid());

💡 Note: UNIQUEIDENTIFIER in SQL Server

Quick Reference Table

| Function | Purpose | |----------|---------| | Numeric Types | Store integer and decimal numbers | | String Types | Store text data | | Date/Time Types | Store dates and times | | Boolean | Store true/false values | | JSON Types | Store JSON documents | | UUID | Store universally unique identifiers |

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