Database Keys

In a relational database, a key is a column or a set of columns that uniquely identifies each row in a table. Without keys, data can become inconsistent, duplicate records can appear, and searching for specific information becomes slow.

Let’s see why we need keys with a real-world example. Imagine running an online store. Your store has grown rapidly, and you now manage thousands of customers, products, and orders. One day, a customer calls in, asking about their recent purchase. You search the customer table but find two records with the same names.

Having a unique column helps, but uniqueness isn’t limited to just a single column. A key can consist of one or multiple columns, ensuring each row remains distinct in the table.

Let’s discuss how we can identify the unique columns:

Identifying unique column

Let’s look at the following customer table. Can you identify which column(s) should have unique values?

Let’s modify this table and make sure the unique data.

Fixing the duplicate records issue