5 SQL interview questions every fresher should practise

Second highest salary
The most repeated SQL question. Use a subquery with MAX. For the Nth highest, use DENSE_RANK() OVER (ORDER BY salary DESC) and filter rank = N.
```
SELECT MAX(salary) FROM employees WHERE salary < (SELECT MAX(salary) FROM employees);
```
Find duplicate rows
Group by the column and filter groups with HAVING. WHERE filters rows before grouping, HAVING filters groups after.
```
SELECT email, COUNT(*) FROM users GROUP BY email HAVING COUNT(*) > 1;
```
JOINs with no match
To find customers who never ordered, use LEFT JOIN and keep rows where the right side is NULL. Use IS NULL, never = NULL.
```
SELECT c.name FROM customers c LEFT JOIN orders o ON c.id = o.customer_id WHERE o.id IS NULL;
```
Practise on real data
Solve Easy problems first and aim for 2 a day. Cover JOINs, GROUP BY, subqueries and window functions.
```
leetcode.com/problemset/database
hackerrank.com/domains/sql
```
Check openings that ask SQL
See today's verified openings, read the skills listed, and match the SQL level to what you are practising. Apply early with official links.
```
hirastra.com/today
```

Skip the searching: today's verified openings are posted three times a day with official apply links, and you can check your resume against any of them with the free ATS checker.

Second highest salary

Find duplicate rows

JOINs with no match

Practise on real data

Check openings that ask SQL