Which key declares that an index in one table is related to that in another?

Solution (By Examveda Team)

This question asks about the type of key that links an index in one table to an index in another table.
Imagine you have two tables: one for customers and one for orders. Each customer has a unique ID, and each order is linked to a specific customer. To connect these tables, we need a key that establishes the relationship between the customer ID in the customer table and the customer ID in the order table.

Let's look at the options:
Option A: primary – A primary key identifies a unique row in a table. It doesn't directly link tables.
Option B: secondary – A secondary key is any index that is not a primary key. It's not used for linking tables.
Option C: foreign – This is the correct answer! A foreign key is a column or set of columns in one table that refers to a primary key in another table. It establishes the relationship between the tables.
Option D: cross – This term isn't used to describe a key in the context of linking tables.

Therefore, the correct answer is Option C: foreign.