If you’ve written SQL for a while, you’ve likely bumped into COALESCE and ISNULL. Both are handy for dealing with NULL values in your tables, swapping them out for something useful. They might seem interchangeable at first, but they’ve got some sneaky differences that can change your results—or even break your query—if you’re not careful. Let’s dig into how they work with real table data, using an Orders table to keep things consistent, so you can see exactly what’s going on.
Setting the Scene: Our Orders Table
To make this relatable, let’s imagine an Orders table with some typical columns: