Data Warehouse Basics

What Is a Data Warehouse?

A data warehouse is a centralized system built specifically for analytics — running large, complex queries across historical data to support reporting and decision-making, rather than powering live application transactions.

Fact and Dimension Tables

Fact tables store measurable events, like an individual sale or click. Dimension tables store descriptive context, like customer names or product categories, that help you slice and filter fact data.

Star Schema Example

-- Fact table: one row per order
CREATE TABLE fact_orders (
    order_id INT,
    customer_key INT,
    product_key INT,
    order_amount DECIMAL(10,2),
    order_date DATE
);

-- Dimension table: descriptive customer attributes
CREATE TABLE dim_customer (
    customer_key INT,
    customer_name VARCHAR(100),
    region VARCHAR(50)
);

Querying this structure lets you answer questions like "total revenue by region" by joining the fact table to its related dimension tables.