This SuiteAnswers article:
Published 03/04/2011 12:24 PM | Updated 09/16/2019 10:37 AM | Answer Id: 10101
Also, the Database SQL Reference: https://docs.oracle.com/cd/B19306_01/server.102/b14200/toc.htm
(You can also just google for the specific function you’re looking for and the specific page you want from this is usually one of the top few results). Not all of the functions in here are guaranteed to work in NetSuite, so the SA article is the best to stick to if you can make those work, but most of these do work, so if you’re really finding the SA choices limiting, this is a good reference.
For specific examples, I would search SuiteAnswers for what you’re looking for using “saved search formula” keywords.