link location to venue
Link venue to location so one doesn't have to manually add the city, as it's already assumed with the venue.

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@Kelly, thanks for the additional comments/suggestions. FYI, I merged "Sidewinder" into "The Sidewinder".
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Kelly McKinnon commented
Yes, also this eliminates duplicates. One of my frequent venues is "The Sidewinder", and I'm never sure whether to choose "Sidewinder" or "The Sidewinder" because people have listed shows under both. While I realize merging is possible, I assume the merge only affects the past, so if one were to re-duplicate it, another merge would be needed, and so on.
There is no reason for the venue/city info to be manual when there are tools available to autocomplete and standardize it. You can still log it in the database the same for analytics purposes.
In a few cases, a venue may not be on Google Maps; to deal with this a backup manual "Couldn't find this venue" option could be available, but it should be clear to users that they should search first. I also think the idea of having a secondary "notes" field for the location is good, as another idea said, since a lot of venues have multiple rooms with varying capacities and features.