See wiki page for an organized selection of many types of queries: https://github.com/UNC-Libraries/III-Sierra-SQL/wiki
See the kms_sql_dump for a mess of queries Kristina had saved in Navicat and didn't want to disappear before she left her position at UNC, since they might be of use to someone. Some of these were used/tweaked daily to analyze our catalog data to make online catalog mapping/transformation decisions, or to find examples. There's a README in that folder giving a little description.