This weird SQL NULL logic cost me hours | SQL 3-valued logic
This simple-looking SQL query tripped me up—and cost me hours to debug.
In this video, I’ll show you how a weird interaction between != and NULL values in SQL can silently break your filters, lead to missing rows, and mess with your data without throwing any errors.
We’ll walk through:
📌 A quick practical QUIZ (WHERE name != 'John')
📌 Why NULL != 'value' doesn't behave the way you think
📌 What three-valued logic is (and how SQL uses it)
📌 How to fix your filters using IS NULL, IS NOT NULL, and COALESCE()
📌 A fun analogy to help you remember this topic
This is one of those SQL quirks that’s easy to miss, even for experienced developers—and much harder to spot when you're working with messy real-world datasets in analytics, business intelligence, or engineering projects.
💬 Have you ever been confused by NULLs in SQL?
Or faced other sneaky SQL behavior that took forever to debug?
Drop your experience in the comments—I’d love to learn from it!
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👋 Hi friend, my name is Eugene and I'm just a dev 👨🏼💻
I've been in tech for 5 years, working as a Data Engineer 📊
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Thanks for watching—and happy coding!