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00:00 Intro
01:04 Origins of the myth
02:00 What does COUNT(*) mean?
02:30 COUNT(*) example
04:00 Primary and secondary indexes in MySQL
05:20 COUNT(id) example
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Stable Diffusion

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Community Picks

Counting rows using COUNT(*) in MySQL is not slow as often believed. It is actually optimized to be the fastest way to count rows.

Stop using COUNT(id) to count rows

Super informative video, it’s a shame PlanetScale let Aaron go as part of their layoffs, but I get it. I think Aaron will be just fine and he has his own YouTube channel too!

So this video is about MySQL. Does it work the same way in PostgreSQL or SQLite, for example?

This is a very good video. I’ve been working with SQL Server for over 15 years now and always heard don’t use Count(). I know that the user was using MySql but I’m assuming this logic flows over to Sql Server as well. Now I know in SQL Server if you do COUNT(column_name) and the value is NULL then it doesn’t count that column. I think I’m going back to Count() . :)

Great video, but why are we even given this argument if the optimizer always replaces it? In what case would you give a column name to <code>count</code>?