Post #2515

✅SQL Mistakes Beginners Should Avoid🧠💻 1️⃣ Using SELECT * • Pulls unused columns • Slows queries • Breaks when schema changes • Use only required columns 2️⃣ Ignoring NULL Values • NULL breaks calculations • COUNT(column) skips NULL • Use COALESCE or IS NULL checks 3️⃣ Wrong JOIN Type • INNER instead of LEFT • Data silently disappears • Always ask: Do you need unmatched rows? 4️⃣ Missing JOIN Conditions • Creates cartesian product • Rows explode • Always join on keys 5️⃣ Filtering After JOIN Instead of Before • Processes more rows than needed • Slower performance • Filter early using WHERE or subqueries 6️⃣ Using WHERE Instead of HAVING • WHERE filters rows • HAVING filters groups • Aggregates fail without HAVING 7️⃣ Not Using Indexes • Full table scans • Slow dashboards • Index columns used in JOIN, WHERE, ORDER BY 8️⃣ Relying on ORDER BY in Subqueries • Order not guaranteed • Results change • Use ORDER BY only in final query 9️⃣ Mixing Data Types • Implicit conversions • Index not used • Match column data types 🔟 No Query Validation • Results look right but are wrong • Always cross-check counts and totals 🧠 Practice Task • Rewrite one query • Remove SELECT * • Add proper JOIN • Handle NULLs • Compare result count SQL Resources: https://whatsapp.com/channel/0029VanC5rODzgT6TiTGoa1v ❤️Double Tap For More