Relational Database

A relational database organizes data into tables made of rows and columns, with relationships expressed through keys. It is typically queried with SQL and enforces data integrity through constraints and transactions.

Why it matters

The relational model suits data with clear structure and relationships, such as customers, orders, and invoices. Keys and constraints stop bad data from entering, joins let you combine tables on demand, and ACID transactions keep related changes consistent. Decades of tooling, drivers, and operational knowledge make it the default choice for most business applications.

Example

customers            orders
id | name            id | customer_id | total
1  | Asha            10 | 1           | 499
2  | Ravi            11 | 1           | 120

orders.customer_id points to customers.id. Asha has two orders, and the data about her is stored only once.

Common mistakes

• Storing comma-separated lists in one column instead of using a related table.
• Skipping foreign keys "for speed" and then discovering orphaned rows later.
• Assuming a relational database cannot scale. Replication, partitioning, and caching take most workloads far.

Related

• Primary key
• Foreign key
• Database normalization
• ACID

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