The G major scale is perhaps the first major scale you should learn as a bassist. The key of G major is a very common choice for songs in all genres of music, and it is simple to learn.
The key of G Major has one sharp. The notes of the G major scale are G, A, B, C, D, E and F#. This key is nice on the bass guitar because all of the open strings are part of it, and the first string is the root.
Besides G major, there are other scales that use the same key (these are modes of the G major scale). Most notably, the E minor scale has the same notes, making it the relative minor of G major. When you see one sharp in the key signature for a piece of music, it is probably in either G major or E minor.
This article goes over how to play a G major scale in various places on the fretboard. You may wish to review bass scales and hand positions before reading on.