I came across someone using a MySQL SET where they really should have been using a many-to-many mapping table. Wanting to know more about SET, though, I decided to open the MySQL documentation and look up SET in the index:
In case you're wondering, every other line if you scroll down reads "SET" with a location of "MySQL 5.0 Reference Manual."
The first and second "SET" all refer to the exact same documentation on "character set." The third bumps it down to information about UTF-8 support, but is generally the same. The remaining twenty-six (!!) all bring you to the SET command for setting database variables.
To be fair, the next entry below SET is "SET data type" which brings up exactly what I wanted, but still - that's kind of ridiculous.