Joe Celko's SQL for Smarties, 3rd Edition

21.4. Extrema Functions

The MIN() and MAX() functions are known as extrema functions in mathematics. They assume that the elements of the set have an ordering, so it makes sense to select a first or last element based on its value. SQL provides two simple extrema functions, and you can write queries to generalize these to (n) elements.

21.4.1. Simple Extrema Functions

MAX([ALL | DISTINCT] <value expression>) returns the greatest known value in the <value expression> set. This function will work on character and temporal values, as well as numeric values. An empty set returns an empty result set. Technically, you can write MAX(DISTINCT <value expression>), but it is the same as MAX(<value expression>); this form exists only for completeness, ...