I revisit the problem of returning a row for each day in a month, and generalize the solution to return rows for any desired range of dates. Then I go further and explore how to return multiple ranges of dates from the same query.

Median is a measure of central tendency useful in describing the typical experience, or the typical case. It's a type of average along with the mean, but less susceptible to skew from outlying values. Median is useful in describing, say, what the typical sale looks like, or what the typical customer is likely to spend.

Oracle Database implements a family of STDDEV functions for computing the standard deviation from the mean. If you think of the mean as beginning to paint a picture of the underlying data, then standard deviation is another brush-stroke toward a fuller picture that will help you draw meaning from the data you're studying.

AVG is an aggregate function in SQL to compute the "average" of a set of values. More precisely, it computes the mean of those values. And even more precisely, AVG computes what is known as the arithmetic mean. But keep reading! Learning about "average" is like uncovering an iceberg. There's more to it than meets the eye.

Thanks to Jim Melton's long-suffering patience at answering more questions than anyone should be allowed to ask, I finally begin to piece together a mental model for how the WITH clause in SQL really works.

A good lesson on why you should always use table aliases. I used to figure it was the database engine's job to sort out which column belongs to which table. That's an attitude that can get you in trouble over wrong results from the queries that you run.