Query for finding keys (IDs) that only have one of two values associated with it

[Sean Griffin]

Hi. I'm a complete newbie with MySQL and need some help creating a query. What I'to do is:
For any post_id that has a _VenueVenue but does NOT have a _VenueLat, return the post_id.

So using my example table below, the query would return 21348 and 21354, because those post_id's have a _VenueVenue (in the meta_key column), but do not have a _VenueLat.

Any assistance would be greatly appreciated.

Thanks,
Sean

meta_id post_id meta_key meta_value
295290 21302 _VenueVenue Wilson State Park Campground
295310 21302 _VenueLat 44.0309908
295882 21348 _VenueVenue Flatbread Company
295938 21354 _VenueVenue Tuck School of Business at Dartmouth College
295206 21296 _VenueVenue Rosewood Park
295226 21296 _VenueLat 42.8962559