[TIL] Junior Web Developer Log - Day 71

TIL

I was unable to write a TIL entry the day before yesterday because of company dinner, and I also could not write one yesterday because I was working from home and had a hospital appointment. Starting today, however, I plan to return to my normal routine.

During my commutes, I listend to the actual final lecture in the SQL section. Last time, I mistakenly thought that the previous lecture had been the last one, but this one truely the final lecture.

In this lecture, I reviewed several important SQL concepts. First, join queires are used to retrieve data by connecting multiple tables, usually through common attributes such as primary keys and foreign keys. I was also reminded that failing to include a join condition can result in a Cartesian product. Second, group queries use GROUP BY to organize data into groups and apply aggregate functions such as COUNT, SUM, AVG, MAX and MIN. In addition, conditions on grouped results are handled with HAVING, and any non-aggregated attribute must be included in the GROUP BY clause. Third, nested queries involve placing one query inside another, so that the result of the inner query can be used by the outer query. In such cases, = is commonly used for single-row results, whereas IN is often used for multiple-row results. I also noted that EXISTS and correlated subqueries are frequently tested. Finally, I reviewed views, which are virtual tables that simplify complex queries and can also be beneficial for security. However, views involving joins or aggregation are often difficult to update.

As for Digital Logic Circuits, I have already studied up to section 3-6, so I now need to begin with section 3-7 on Youtube. In that sense, today’s study was essentially a review.

For exercise, since it was both a Push and Pull day, I did pull-overs, frog pull-ups, the dumbbell press, the wide lat pulldown, the inner press, the one arm seated row and the chest press.