Hi there,
Table creation I think is something you can easily learn, but extremely hard to master. Depending on what you want to do with your table, how you want it the inherent with other table or even the core tables. Then there is the side of reporting on the table and Database view (joints) with other tables.
Depending on your starting knowledge of database tables, if you are comfortable to SQL tables, you might be able to start off with getting a PDI (personal development instance) from ServiceNow for free and start playing around with it. Getting yourself comfortable is the table layout, how to create new table and how they interact with other tables.
Do know this, everything on ServiceNow is stored in a table somewhere. So needing to know all the tables and what they do is like saying learning all the ins and outs of ServiceNow, something that can only come in time using ServiceNow and not by reading some online manual.
Hope this helps.
Joe
