Tips for Writing SQL Queries

In my previous job, I had a basic grasp of writing a SQL query, but I was never quite comfortable with “advanced” queries. (By “advanced”, it’s more like intermediate at best — it’s the nuances of joins, group-bys, having vs. where.) I was told that whatever SQL I didn’t know would be “easy” to pick up and would happen naturally, although in practice that never quite happened. It wasn’t until I started to come up with a system for solving interview-style programming problems that I started to similarly come up with a system for writing any SQL query. The following is the result, which is less of a “tutorial” for “beginner SQL” and more of a systematic process for constructing a SQL query:
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