Today I focused on filtering posts by category. This proved much more difficult than expected, because I wanted to store my categories in a separate DB table which linked to a dropdown menu on the "Create a post" page.

My category table fields are pictured below

The category is then joined onto the post table, in the field 'categoryString'. As you can see this uses a foreign key. Because of this, I couldn't filter by constraints - Bubble found a reference to category instead of a string it could filter by within constraints. Finally I updated the categoryString to be a text string, so that I could simply copy the foreign key and use it as a text constraint.

After about 3 hours of googling, looking at Bubble tutorials and reading endless forums about this sort of thing, I finally came across the solution. In this case it was necessary to use an advanced filter.