SQL Mistakes We All Made in 2025 !

 As we reach the end of the year, it’s time for a little reflection.

If you’re a SQL developer, chances are you wrote a lot of SQL in 2025. And along the way… let’s be honest — a few mistakes probably slipped in. Some small. Some… not so small.

The good news?
You’re definitely not alone.

Let’s walk through some of the most common SQL mistakes developers made this year — and what we can learn from them.

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1. Running DELETE Without a WHERE Clause

Yes… it happened.

Someone ran a DELETE query in production without a WHERE clause.
And yes — I’ve seen this happen more than once in real life.

💡 Lesson learned:
Always test destructive queries using a transaction:

BEGIN TRANSACTION;
DELETE FROM table_name WHERE condition;
ROLLBACK; -- or COMMIT when you're 100% sure

This one habit alone can save your job.

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2. Googling LEFT JOIN vs RIGHT JOIN (Again…)

Let’s be honest — we’ve all done this.

And that’s okay.

Even experienced developers Google things all the time. SQL isn’t about memorization — it’s about understanding patterns.

💡 Pro tip:
Practice is the only real fix here. The more queries you write, the more natural joins become.

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3. Writing an Unformatted SQL Query

You know the one:

• No line breaks
• No aliases

One massive unreadable block of SQL

And yes… I still do this sometimes too.

But the moment you open someone else’s unformatted query — that’s when it hits you how painful it really is.

💡 New Year’s Resolution:
Let’s all format our SQL.
Your future self (and teammates) will thank you.

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4. Using Functions in the WHERE Clause

Functions are great — until they kill your performance.

Using a function on an indexed column prevents the database from using that index, which often leads to slow queries.

❌ Bad:

WHERE YEAR(order_date) = 2025

✅ Better:

WHERE order_date >= '2025-01-01'
  AND order_date < '2026-01-01'

💡 Rule of thumb:
Avoid wrapping indexed columns in functions when filtering.

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5. Optimizing One Query… and Breaking Five Others

Indexes are powerful — but too many can backfire.

Adding unnecessary indexes can:

• Slow down inserts & updates
• Increase storage usage
• Confuse the query optimizer

💡 Remember:
Every index has a cost. Create them intentionally.

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✅ Final Thought

If you recognized yourself in any of these — relax.
You’re not bad at SQL. You’re learning.

Mistakes are part of the journey, even for experienced developers.

👇 Now your turn:
Which SQL mistake did you make this year?
Drop it in the comments — let’s learn together.