Great toy but it's a bit misleading not to touch on the query planner. All real SQL implementations will plan how to most efficiently run a query so the order o

Great toy but it's a bit misleading not to touch on the query planner. All real SQL implementations will plan how to most efficiently run a query so the order of operations can be wildly different to expected based on the data and indexes available. This kind of tutorial makes it look like joins are very inefficient whereas a real database may make them highly efficient for a given query.