GlideQuery from Quebec is now installed by default on every ServiceNow instance.
This is a short cheat sheet to make the best use of it. All examples use the tables of the ITBM module.
These are the main sources of information used:
Overview of GlideQuery by Samuel Meylan and his cheat sheet
Official ServiceNow Docs
ServiceNow Developer blog post made by Peter Bell, creator of GlideQuery
Read only one record
Read records with complex where and or conditions
Check if record exist
Create record and return sys_id
Example of filter and result manipulation