Writing "categories left join posts" instead of "categories join posts" worked for me.

i did something similar at the beginning to account for mr. mrs. miss. md . phd. sr. and all that, but for some reason the code still works without taking into account these things. in this specific code you just need to take into account the two variants i.e. first-name last-name and last-name, first-name

Encountered the same problem, using right join fixed it.