Question

We have a vehicles table that has a VehicleName column. I’m looking into a bug where a user has multiple vehicles of the same VehicleName. I have this query to help return which VehicleNames have been used multiple times:

SELECT VehicleName, 
 (
  SELECT count(VehicleName) 
  FROM Vehicles as V2 
  WHERE V1.VehicleName = V2.VehicleName
 )
FROM Vehicles as V1;

For one thing, it’s slow. That’s not too bad because this isn’t going into production; it’s just to aid in a bug fix. Second, this will return every VehicleName, even the ones that have a count of one, those are VehicleNames I’m not interested in for this application. I can’t remember how to name the subquery, so I can’t add a where to limit it.

I’m interested not just in how to name the subquery, but also are their faster solutions to this?

Answer 1

Are you trying to do this in some ugly way ?

SELECT VehicleName, COUNT(*) as TOTAL
FROM Vehicles
GROUP BY VehicleName
HAVING TOTAL > 1
ORDER BY TOTAL DESC;