Multiple categories for items

i've seen a lot of different solutions for this and i'm wondering what /prog/ uses

when you have items in a database and each item needs to be able to belong to multiple categories, so obviously you have a column for categories, or in some cases even a table in it's own lol, but how do you encode the values of each items parent categories?

i've been leaning mostly towards serializing it but maybe there's a better way that i'm missing

wow now i'm not the one to make note of this because i've used /prog/ for so long and just looked through all the trolling and bullshit, but srsly gais

it used to be that you could ask a serious question here and you would get trolled but not THIS much, now it's just like someone is running automatic bots on the site posting random memes in every thread