Understanding Lookup Logic

Lookups retrieve related information from another table based on a shared identifier. In business models, data is rarely stored in one large table. Instead, it is structured across separate tables that are connected by a key. A key is a unique value that links records between tables. For example:

• Employee ID links employee details to salary records;
• Product ID links products to pricing tables;
• Customer ID links customers to order history.

Lookup functions allow Excel to search for a value in one table, find the matching key and return related data from another column

There are two primary matching strategies:
Exact match: used when identifiers must match perfectly such as IDs or codes;
Approximate match: Used when working with ranges such as tax brackets or discount tiers.

Understanding this logic is more important than memorizing formulas. If the structure is correct, the lookup will work. If the structure is broken, the formula will fail.

Example

Imagine two tables:

Table 1 Employees

Table 2 Salaries

The shared key is Employee ID. A lookup retrieves salary from Table 2 and places it next to employee data in Table 1.

This is relational thinking.