🚨 SQL Fact Most Beginners Learn Too Late!

Many aspiring Data Analysts think these two SQL commands do the same thing... but they don't. 👇

📌 UNION

✅ Combines results and removes duplicates.

📌 UNION ALL

✅ Combines results and keeps duplicates.

Example:

Table A:

101
102
103

Table B:

103
104
105

🔹 UNION → 101, 102, 103, 104, 105

🔹 UNION ALL → 101, 102, 103, 103, 104, 105

💡 This small difference can affect both your query results and performance. In fact, UNION ALL is usually faster because SQL doesn't need to remove duplicates.

🎯 A favorite SQL interview question that catches many beginners off guard!

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