Back to the SQL

This week was mostly a refresher for me, which was honestly kind of nice. A lot of the week was spent working with COUNT, AVG, GROUP BY, HAVING, and different types of joins. None of those concepts felt completely new, but I definitely had a few moments where I had to stop and remind myself of the little details. One example was the difference between COUNT(*) and COUNT(column_name). I knew that NULL values could affect results, but seeing COUNT(column_name) used with a LEFT JOIN to produce a count of zero made the behavior much easier to remember.

I also got some good practice with WHERE versus HAVING. I already knew that WHERE filters rows and HAVING is used with grouped results, but actually working through multiple problems that required one or the other helped reinforce when each belongs in a query.

The second SQL homework was probably the most interesting part of the week because some of the questions required combining several ideas at once. The GPA query was the most involved. It required joining multiple tables, calculating a credit-weighted average, handling NULL grades correctly, and still including students who did not have a calculated GPA. It was a good reminder that even when the individual pieces of SQL are familiar, combining them correctly can still take some thought.

This week felt less like learning SQL from scratch and more like getting back into the rhythm of it. I am definitely feeling more comfortable reading a problem, figuring out what data I need, and building the query from there again.