You don't need a paid course to get interview-ready in SQL. You need the right free sites, in the right order.
Learn first, then type a lot, then do interview questions. One site at a time.
Pick one. Start today.
Learn: start here
Practise: then type a lot
- 03
Select Star SQL
selectstarsql.com. A free interactive book built on one real dataset.
- 04
PostgreSQL Exercises
pgexercises.com. Joins, aggregates and recursive queries on a club booking database.
Interview: then real questions
- 05
LeetCode SQL 50
leetcode.com. Free study plan of 50 interview-style SQL problems, easy to medium.
- 06
DataLemur
datalemur.com. SQL questions tagged by company. Free questions to start.
The 5-week order
| Week | Use | Goal |
|---|---|---|
| 1 | SQLBolt | Basics + JOINs |
| 2 | SQLZOO + Select Star | Subqueries |
| 3 | pgexercises | Aggregates |
| 4 | LeetCode SQL 50 | Interview style |
| 5 | DataLemur | Company questions |
How to use them
Wastes time
- Reading answers first
- Jumping between all 6
- Copy-pasting queries
Works
- Try 10 minutes before a hint
- One site at a time
- Type every query yourself
Want a 7th? The SQL playground on this site has 50 interview questions on Indian sales data, checked instantly. Free, no sign-up.