Relational databases store data in structured formats using tables, which are organized into rows and columns. Each table represents a different entity, such as users, products, or orders. The columns define the properties of that entity, such as a user's name, email, or registration date. Each row in a table represents a specific instance of the entity, often referred to as a record. For instance, in a users table, one row might hold information about a specific user, including their name and email address. This tabular format allows for easy data retrieval using queries.
To maintain relationships between different tables, relational databases use keys. A primary key uniquely identifies each record in a table, ensuring that no two records are identical. For example, a user ID might serve as a primary key in a users table. Foreign keys are used to link records across tables. For instance, in an orders table, a foreign key might reference the user ID from the users table to connect a specific order to the user who made it. This structure allows developers to model complex relationships and perform operations like joins, which can combine records from multiple tables based on related keys.
Data integrity is a key feature of relational databases, often enforced by constraints. These constraints ensure that data adheres to defined rules, preventing issues like duplicate entries or invalid data types. For instance, a constraint might ensure that an email address must be unique in the users table, helping maintain data quality. Additionally, transactional support, through the use of ACID properties (Atomicity, Consistency, Isolation, Durability), ensures that database operations are reliable, even in the event of errors or system failures. Overall, relational databases provide a well-organized and efficient way to store, retrieve, and maintain data.