Introduction
This 5-minute read will introduce you to the fundamentals of data warehousing, covering key concepts like the difference between a database, data warehouse, data mart, and data lake, OLAP vs. OLTP, ETL vs. ELT processes, the layers of a data warehouse, and the basics of dimensional modeling.
Difference between Database, Data Warehouse, Data Mart, Data Lake
A Database is like a digital filing cabinet, storing organized data for specific tasks, like managing customer orders. A Data Warehouse is a larger storage system designed to hold data from multiple sources, structured for analysis. A Data Mart is a focused version of a data warehouse, serving specific business functions. A Data Lake is a vast storage space for raw data, both structured and unstructured, awaiting further processing.
What is OLAP and OLTP?
OLTP (Online Transaction Processing) manages everyday operations like processing transactions quickly and efficiently. OLAP (Online Analytical Processing) helps in analyzing large volumes of data to identify trends and patterns, supporting decision-making.
ETL and ELT Processes
The ETL process involves Extracting data from sources, Transforming it to meet specific standards, and Loading it into a data warehouse. The ELT process is similar, but the data is Loaded first and Transformed afterward, often used when dealing with large datasets.
Various Layers of a Data Warehouse
- Staging Layer: Temporary storage for raw data from different sources.
- Data Integration/Transformation Layer: Data is cleaned and organized here.
- Data Storage Layer: The final, structured home for the transformed data.
- Data Access/Presentation Layer: The interface where users access and analyze the data.
Dimensional Modeling: Fact and Dimension Tables, Star Schema, and Snowflake Schema
Dimensional Modeling structures data to make it easy to access. Fact Tables store measurable data, like sales figures. Dimension Tables store descriptive data, like product names. In a Star Schema, the fact table is central, surrounded by dimension tables. A Snowflake Schema is a more complex version where dimension tables are further normalized.