A relational database is a type of database that stores information in tables made up of rows and columns. Different tables can be connected to each other through relationships using keys. For example, a Customers table can contain customer information while an Orders table contains order information. A CustomerID column can be used to connect the customer to their orders. This relational structure allows information to be stored separately while still making it possible to combine the information when required.
Most SQL learning is based on relational database concepts. Understanding relationships between tables is essential for learning primary keys, foreign keys, joins, normalization, and advanced SQL queries.
An e-commerce company may have Customers, Orders, Products, and OrderDetails tables. The Customers table stores customer information, while the Orders table stores orders. A CustomerID can connect a customer to all orders placed by that customer.
SELECT
c.CustomerName,
o.OrderID
FROM Customers c
INNER JOIN Orders o
ON c.CustomerID = o.CustomerID;Banks may maintain separate Customers, Accounts, Transactions, and Branches tables. A Data Analyst can combine information from these tables to create reports about customers, accounts, and transactions.
- Relational databases store data in tables.
- Tables contain rows and columns.
- Tables can have relationships with other tables.
- Primary keys identify records.
- Foreign keys connect related tables.
- SQL is widely used with relational databases.
What is a relational database?
A relational database stores data in tables and establishes relationships between those tables using keys.
Why are relationships important in a relational database?
Relationships allow related information stored in different tables to be connected and retrieved together when required.