Searching large sqlite tables for static values (and how to generate a fake table)

This is my first time building a 'large scale' sqlite database (~20,000 entries in a table). Some of my fields are always going to be a static value. For example, if I had a field 'difficulty' and it was always going to be either 'easy, medium, or hard', would making the difficulties integers (1, 2, 3) speed up searches by difficulty? I would think it would, but I'm not sure if the speed is going to be noticeable.

My real goal is to test this. But without manually creating 20,000 insert statements I'm not sure how. Is there a way to generate in bulk 'fake' values in an sqlite table?