Subquery or CTE? Here’s How I Decide.
The simplest way to make your SQL cleaner, faster to debug, and easier to explain.
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If you’ve written SQL long enough, you’ve probably hit that moment where your query stops making sense halfway through.
You’re scrolling up and down, trying to remember which brackets belong together, and wondering if maybe Excel wasn’t so bad after all.
I used to write those kinds of queries too: one giant nested block that did technically work but terrified anyone (and my future self!) who had to read it later.
Then I started using common table expressions (CTEs).
And no, they don’t make your query faster. Performance is not that improved.
But they do make your queries readable.
In my latest post, I break down:
When to use a subquery vs. when to switch to a CTE.
What’s actually happening in the background.
And a few small readability habits that make your future self’s life easier.
If you’ve ever opened one of your own old queries and wondered, “Who the heck wrote this?”, this post will help.
Read it here:
P.S.: If you liked this post, you’ll probably like my SQL Best Practices Guide too.
It’s full of the little formatting habits and conventions that make your code easier to read, review, and explain, especially when someone asks you to “just make a quick change.”
Grab yours here!
Till next time,
— Sarah
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Thanks for reading!
—Sarah
