What is a Database?
- A database is a place to store data.
- A relational database system (RDMS) stores data in tables.
- Each table has rows and columns, much like a spreadsheet.
- Each row has one or more columns to store data values.
What is SQL?
- SQL is a language used to retrieve and manipulate data in a RDMS.
- SQL stands for Structured Query Language.
- SQL is pronounced as S.Q.L. (ess-cue-ell) or as Sequel. They are used interchangeably.
Relational Database Tables
As an example, 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.
SQL is the language with which you retrieve data, update data, and remove data.
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 with information on Products, Suppliers, Customers, and Orders.
Below is an Entity Relationship Diagram (ERD) which shows the tables and their relationships.