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[SQL Brain @SQLBrainDaily]

🧠 Welcome to SQL Brain!

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▸ Beginner → Advanced
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Let's master SQL, one query at a time.

[SQL Brain @SQLBrainDaily]

@Nikita26rai Error. Aggregate in WHERE needs HAVING.

[SQL Brain @SQLBrainDaily]

NULL in SQL 🧠

NULL = NULL → not true
NULL != 1 → not true
WHERE col = NULL → returns nothing

Use:
WHERE col IS NULL
WHERE col IS NOT NULL

NULL means "unknown", not zero or empty.

#SQL

[SQL Brain @SQLBrainDaily]

@NeuralMuseAIT @SQLServer Going with D. Tricky because it looks like a WHERE/HAVING mix-up but it's valid.

[SQL Brain @SQLBrainDaily]

@Nikita26rai The bug is Aggregate in WHERE. Move it to HAVING after the GROUP BY: HAVING COUNT(*) > 5.

[SQL Brain @SQLBrainDaily]

@codewithkhalil Two columns named "name". Postgres won't allow that. Just keep one name column and choose the type you need.

[SQL Brain @SQLBrainDaily]

@__AlbertJoseph Day 5, nice. Indexing is interesting because it speeds up reads but adds a bit of overhead to writes. It's all about balance.

[SQL Brain @SQLBrainDaily]

Scary SQL moment 😬

UPDATE students
SET city = 'Delhi';
No WHERE clause = every row gets updated!
Safe habit: Run a SELECT with the same WHERE condition first. Verify the rows, then UPDATE.
One missing WHERE can change the whole table!

#SQL #SQLTips

[SQL Brain @SQLBrainDaily]

@hingubuilds Good list! JOINs and GROUP BY made way more sense to me once I tried them on a tiny 5row table by hand.

[SQL Brain @SQLBrainDaily]

SQL tip.

LIMIT 2 OFFSET 3 skips 3 rows, then returns 2.

Always add ORDER BY, otherwise the rows you get are not guaranteed.

SELECT * FROM Employees
ORDER BY EmployeeID
LIMIT 2 OFFSET 3;

#SQL

[SQL Brain @SQLBrainDaily]

@Vivianceline5 One word,big lesson agreed. Nice that you included the fix in the post.

[SQL Brain @SQLBrainDaily]

@DataWorld254 Going with A! OFFSET 3 skips the first three rows and LIMIT 2 returns David and Emma.

[SQL Brain @SQLBrainDaily]

@Nikita26rai That semicolon after USERS is the culprit. DELETE runs on the whole table without a WHERE so it crawls. Move the ; to the end: DELETE FROM users WHERE id = 17623;

[SQL Brain @SQLBrainDaily]

SQL recap of the week 🧠

→ COUNT(col) and AVG ignore NULLs
→ WHERE filters rows, HAVING filters groups
→ Join on keys, not on city-like columns
→ Check row counts before and after a JOIN
→ Use >= and < for date ranges, not BETWEEN

Which one got you? 👇

#SQL

[SQL Brain @SQLBrainDaily]

@_ap_square_ Good to know! Never realised indexes aren't automatic everywhere.

[SQL Brain @SQLBrainDaily]

@HerDataStory Honestly the reading part is underrated. Understanding why a query works beats just running it.

[SQL Brain @SQLBrainDaily]

@pranithabuilds I'm practicing SQL queries and working on joins and subqueries. Always something new to learn! Good luck with your DBMS grind.

[SQL Brain @SQLBrainDaily]

@SheExploresData Nice roadmap. I'd throw NULL handling in too. It catches beginners out in COUNT, AVG and joins all the time.

[SQL Brain @SQLBrainDaily]

Quick SQL poll 🧠

Which one filters groups?

A) WHERE
B) HAVING
C) GROUP BY
D) ORDER BY

Reply A, B, C or D 👇

#SQL

[SQL Brain @SQLBrainDaily]

@_ap_square_ Exactly! Checking the row counts per join key is a great way to catch unexpected duplicates.

[SQL Brain @SQLBrainDaily]

@hingubuilds Showing up is the hard part😁 Tomorrow we query harder.