SQL Tutorial: Introduction

What is SQL?
  • SQL is a language used to retrieve and manipulate data in a RDMS.
  • SQL stands for Structured Query Language.
What is a Database?
  • A database is a place to store data.
  • A relational database system (RDMS) stores data in tables.
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Relational Database Tables



A relational database stores data in tables. Each table has a number of rows and columns.

The table below has 4 rows and 3 columns.






SQL and Relational Databases


A relational database contains tables which store data that is related in some way.
SQL is the language that allows retrieval and manipulation of table data in a relational database.


The database below has 2 tables: one with data on Users and another with data on Products.







Example database


This tutorial uses a database which is a modernized version of Microsoft's Northwind database. Northwind is a fictitious store that sells specialty food products from all over the world. The database has 5 tables.


Below is an Entity Relationship Diagram (ERD) which shows the tables and their relationships.

Additional details of the data model are available on the Sample Database page.
You can also 'play' with the database directly from your browser using our SQL Sandbox.