By the end of this page you can say, out loud and in your own words, what every core piece of SQL does. What a table and a row really are. The six clauses, and the order they actually run in, which is not the order you type them. NULL, and why it breaks comparisons. Filtering, aggregation, GROUP BY and HAVING. Joins. CASE. Subqueries, CTEs and window functions. Keys and indexes. That list is most of what an analyst job, an interview, and a first real dataset will ask of you.
Here is what to actually do with it. Go through once end to end without stopping, just for the shape. Then come back to the retrieval sheet near the bottom, cover the right-hand column, and try to say each answer before you read it. That second pass is where the learning happens, and there is measured evidence for it further down.
The short version: SQL is one sentence with six parts, and every part answers a different question about your rows. Learn what each part does and where it runs, and the rest is vocabulary.
One idea decides more of your SQL experience than any other, so it gets the picture. You write a query in one order. The database runs it in a different order. Almost every confusing SQL error is that gap.
