Designing Efficient Data Models

# Designing Efficient Data Models

## **1. Introduction**
This tutorial aims to guide you through the basic concepts of designing efficient data models, with a particular focus on star schema and snowflake schema. By the end of this tutorial, you should have a good understanding of these concepts and know when to use each. 

**Prerequisites:**
A basic understanding of databases and SQL is required for this tutorial.

## **2. Step-by-Step Guide**

### **Concepts**
- **Star Schema:** A star schema (also known as star-join schema, data cube, or multi-dimensional schema) is the simplest style of data mart schema and is the approach most widely used to develop data warehouses and dimensional data marts.
- **Snowflake Schema:** The snowflake schema is a more complex data warehouse model than a star schema, and it is a type of star schema. It is called a snowflake schema because the diagram of the schema resembles a snowflake.

**When to use each schema**
- **Star Schema:**
  - Use when you need fast aggregation and simpler queries, at the expense of data redundancy.
- **Snowflake Schema:**
  - Use when you want to eliminate data redundancy and improve data integrity, at the cost of more complex queries and slower performance.

## **3. Code Examples**

### **Example 1: Star Schema**

Here is an example of creating a star schema in SQL:

```sql
-- Fact Table
CREATE TABLE Sales (
    ProductID int,
    OrderDate date,
    SalesAmount decimal
);

-- Dimension Tables
CREATE TABLE Product (
    ProductID int,
    ProductName varchar(255),
    ProductCategory varchar(255)
);

CREATE TABLE Date (
    OrderDate date,
    Month varchar(255),
    Year int
);

-- Fact Table
CREATE TABLE Sales (
    ProductID int,
    OrderDateID int,
    SalesAmount decimal
);

-- Dimension Tables
CREATE TABLE Product (
    ProductID int,
    ProductName varchar(255),
    ProductCategoryID int
);

CREATE TABLE Category (
    CategoryID int,
    CategoryName varchar(255)
);

CREATE TABLE Date (
    OrderDateID int,
    Day int,
    Month int,
    Year int
);