What is a reference table?

A reference table is a table used to look up values. It's essentially a lookup table that provides a quick way to find related information. Instead of calculating or deriving a value, you find it pre-calculated and stored in the reference table. This is much more efficient than computing the value repeatedly.

Here's a breakdown of its key characteristics:

* Purpose: To store pre-calculated values or mappings between different values.

* Structure: Typically simple, with a small number of columns. Often it has a key column (or columns) to look up information, and one or more columns containing the related information to be retrieved.

* Use: Used to improve performance by avoiding redundant calculations or complex logic within other parts of a system. It also improves data consistency as the same values are used throughout the system.

* Examples:

* Tax rates: A table mapping income brackets to tax rates. You input income and look up the corresponding tax rate.

* Product codes: A table mapping product codes to product names and descriptions.

* Currency conversion: A table mapping currency codes to exchange rates.

* State codes: A table mapping state abbreviations to full state names.

* Unit conversion: A table mapping between different units of measurement (e.g., kilograms to pounds).

In database systems and programming, reference tables are frequently used to enhance performance and data integrity. They help to reduce data redundancy and make it easier to manage and update data consistently. They're often joined with other tables to retrieve information.