Spot the SQL trap before your interviewer does.
3 traps from real analyst interviews. Each query looks right. Run it, watch the table act it out, and decide: is the number right?
Or browse 27 free interview questions →- 1Trap 1
Revenue - 2Trap 2
Duplicates - 3Trap 3
NULLs - Keep your
streak
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Made by Mohit Khandelwal, 5+ years in analytics. Each trap is a classic SQL mistake: the query runs, and the number still looks right. Read the story
Ratta nahi, riyaaz.
What's the total revenue from Mumbai? This query looks right.
| order_id | customer | city | amount | status | coupon |
|---|---|---|---|---|---|
| 101 | Asha | Mumbai | 1200 | completed | NEW10 |
| 102 | Ravi | Mumbai | 800 | cancelled | NULL |
| 103 | Asha | Mumbai | 500 | completed | NULL |
| 104 | Neha | Delhi | 900 | completed | FEST |
| 105 | Kabir | Mumbai | 300 | completed | NULL |
| 106 | Ravi | Pune | 700 | completed | NULL |
SELECT SUM(amount) AS revenue FROM orders WHERE city = 'Mumbai';
Runs in your browser in about a secondRuns in your browser. Edit it, or just run it first.
Made by Mohit Khandelwal, 5+ years in analytics. Each trap is a classic SQL mistake: the query runs, and the number still looks right. Read the story
Ratta nahi, riyaaz.
Press Run
No account, no setup. The query runs on 6 rows you can see.
SELECT SUM(amount) AS revenue FROM orders WHERE city = 'Mumbai';Run
The table acts it out
Rows light up as SQL picks them. You see 1,200 + 800 + 500 + 300 add up.
| customer | amount | status |
|---|---|---|
| Asha | 1200 | completed |
| Ravi | 800 | cancelled |
| Asha | 500 | completed |
| Neha | 900 | completed |
| Kabir | 300 | completed |
| Ravi | 700 | completed |
“Is 2,800 right?”
Decide before you fix. Hint: look at the status column.
27 more interview questions. Free, no sign-up.
Same idea: a small table, a query that looks right, a trap. Your XP from these counts too.
Find the second highest salary
The tie that breaks LIMIT 1 OFFSET 1.
Try it, free →Know what you don't knowCustomers who never ordered
Why NOT IN returns nothing when the list has a NULL.
Try it, free →Count rows before you add themWhy SUM is too big after a JOIN
One order, several rows: the total is added twice.
Try it, free →Decide what a tie meansNth highest salary
ROW_NUMBER vs DENSE_RANK when people share a salary.
Try it, free →Check what's missingMonth-over-month change with LAG
LAG compares rows, not months. What if a month is missing?
Try it, free →Decide what a tie meansTop 3 salaries in each department
PARTITION BY, and who gets dropped on a tie.
Try it, free →What you keep when you sign in
Your streak
A streak day is 20 XP (two traps). Come back tomorrow to make it 2 days.
+10 XP a trap
From the 3 traps and the free questions. Saved to your profile, on any device.
325 questions
Plus 28 lessons and timed level tests, on 35 messy business tables. Free.
What ChaturIQ is
A free website for learning SQL and practising for analyst interviews. It has 28 lessons, 325 practice questions with every trap explained, and timed level tests, all on 35 realistic business tables. Everything runs in your browser; there is nothing to install or pay for.
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