Oracle SQL Tips
I often am in the middle of some off-the-cuff query and run into one of those technical "gotchas" like a failed compare between two text strings due to trailing spaces or that alter table syntax to modify a column name.
Instead of googling for the answer each time, I've consolidated the websites that I use to find the answers to these common SQL questions and have listed these below for my own and others reference.
Oracle FAQ
Oracle Cheat Sheet
Oracle User Guide
These are the most frequently used resources. I may add to this later but the above will solve most all of your Oracle SQL questions.