HelloSQL: Learn & Practice SQL

SQL tends to make sense while you're reading about it, then fall apart the moment you try to write it yourself. HelloSQL is for the writing part. You read a problem, write a query, and run it. The results show up as a table, and if they're right, it's marked correct right away. Grading looks at what your query returns, not how it's written, so your query doesn't have to match ours. There are 120 exercises, and most of them look like everyday reporting tasks. For example: "List payments from largest to smallest. If two amounts are the same, put the older one first." The practice data is built around an online store's orders, employee attendance, and billing for a subscription service. What's free and what isn't The first 30 exercises are free, and you don't need an account. They cover SELECT, WHERE, ORDER BY, and LIMIT. The other 90 move on to aggregate functions, GROUP BY, HAVING, INNER…