Why Your SQL Query Is Slow | 5 Mistakes Nobody Tells You

Описание: Have you ever written a SQL query that works perfectly… but takes minutes or even hours to run?

In real production systems, I’ve seen one small SQL mistake turn a 10-second query into a 2-hour job.

In this video, I break down 5 real SQL mistakes that silently kill query performance — and how execution plans reveal what’s really happening under the hood.

These are NOT textbook examples.
These are real issues I’ve seen in production databases like Oracle, Amazon Redshift, and PostgreSQL.

📌 In this video, you’ll learn:
• Why SELECT * hurts performance
• How functions in WHERE clauses break indexes
• The danger of missing join conditions
• How missing indexes cause full table scans
• Why execution plans are your best debugging tool

This video is useful for:
✔ SQL Developers
✔ Data Engineers
✔ Backend Engineers
✔ Anyone preparing for SQL interviews

⏳Chapters:
00:00 Why SQL queries become slow
00:34 Mistake 1 – SELECT *
01:11 Mistake 2 – Filtering after join instead of before
02:22 Mistake 3 – Functions on indexed columns
03:18 Mistake 4 – Missing or wrong join conditions
04:00 Mistake 5 – Ignoring execution plans
05:16 Key takeaways
05:24 Interview and Production tip


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