🔥 SQL Interview Concept You MUST Know: CASE WHEN

CASE WHEN is one of the most commonly used SQL concepts for creating conditional logic inside your queries.

It lets you categorize, transform, and analyze data without modifying the original table.

📌 Key points:

🔹 CASE WHEN → Adds IF-ELSE logic to SQL
🔹 Creates custom categories based on conditions
🔹 Works with SELECT, ORDER BY, GROUP BY, and aggregates
🔹 Makes reports more meaningful and easier to understand
🔹 Ends with END to return the final result

💡 Common interview use cases:

✅ Categorizing customers by spending
✅ Creating salary or age bands
✅ Replacing NULL or missing values
✅ Building custom status labels
✅ Conditional aggregations using SUM() or COUNT()

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