I’m working with a Rails 3 application and need help with an Active Record query. I want to create a summary that shows unique values from a database column along with how many times each value appears.
My situation:
I have a users table with a location field that contains city names like: austin, denver, seattle, austin, miami, austin, denver
What I want to achieve:
austin 3
denver 2
miami 1
seattle 1
I know I could loop through all records and count them manually, but I’m wondering if there’s an efficient way to handle this directly with SQL or Active Record methods. What’s the best approach to group these values and get their counts in one query?
Oh nice! try User.group(:location).count - that should do exactly what u need. Are u displaying this or using it for analytics? Just wondering about performance if u’re dealing with lots of data.
yep, User.group(:location).count is the right approach. just heads up - any nil values in the location field will show as blank keys in your hash. toss in .where.not(location: nil) if that’s gonna mess things up for you.
Indeed, using User.group(:location).count is an efficient approach for this. It executes a SQL query with GROUP BY location and COUNT(*), providing a much quicker solution than manually counting records in Ruby. The result will be a hash with locations as keys and their counts as values. If you need the results sorted by count, simply implement .order('count_all DESC') prior to the count method. For large datasets, consider adding an index on the location column for improved performance.