Basically, I have a dataset that is a list of internal location identifiers attached to an ID (so each 'set' of geographical points has its own ID). So an 'id' column and a 'location' column exist in the table.
I need a way to find an ID which contains two different locations, that is:
ID | location -------------- 1 | a 1 | b 1 | c 2 | a 2 | c 2 | d
If I looked for 'a' and 'd', I would get 2.
If I looked for 'a' and 'b', I would get 1.
If I looked for 'a' and 'c', I would get either 1 or 2.
I am using PostgreSQL 9.4.