01
What is the difference between WHERE and HAVING?
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WHERE filters rows before grouping. HAVING filters groups after GROUP BY and can use aggregates like SUM() or COUNT().
SQL Interview Questions for Data Analyst
7 SQL questions with answers for data analyst roles. Tick what you have solved to track your progress.
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02
Find the second highest salary in SQL.
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SELECT MAX(salary) FROM emp
WHERE salary < (SELECT MAX(salary) FROM emp);
-- or: DENSE_RANK() OVER (ORDER BY salary DESC) = 2
03
RANK vs DENSE_RANK vs ROW_NUMBER?
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ROW_NUMBER gives a unique sequence. RANK gives ties the same rank and skips the next (1, 1, 3). DENSE_RANK gives ties the same rank without gaps (1, 1, 2).
04
Write SQL for a running total of sales by date.
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SELECT order_date,
SUM(amount) OVER (ORDER BY order_date) AS running_total
FROM sales;
05
Find customers who ordered in January but not in February.
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SELECT DISTINCT customer_id FROM orders WHERE month = 'Jan'
EXCEPT
SELECT customer_id FROM orders WHERE month = 'Feb';
06
INNER JOIN vs LEFT JOIN — with an example.
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INNER JOIN returns only matching rows. LEFT JOIN returns every row from the left table and NULLs where the right table has no match — e.g. all customers, including those with no orders.
07
What is a CTE and when would you use one?
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A Common Table Expression (WITH name AS (...)) is a named temporary result used inside one query. Use it to break complex logic into readable steps or for recursive queries.