MySQL NULL vs. 0: Which Saves More Space? A Deep Dive with a Billion Rows

In MySQL database design, should you use NULL or 0 to represent 'no value'? This is a classic debate. This article provides a deep dive into the storage space differences between an `INT` field with a NULL value versus a 0, using a one-billion-row case study. You might be surprised to learn that using NULL can save you nearly 4GB of storage in certain scenarios. We will detail MySQL's internal mechanism for storing NULL values and offer trade-off advice regarding performance and query efficiency to help you make optimal design decisions.