sum

Calculates the sum of values on a given column. The value is returned with the same data type of the column, 0 if there’s no row. See #calculate for examples with options.

Person.sum(:age) # => 4562

When given a block, calls the block with each record in the relation and returns the sum of initial_value_or_column plus the block return values:

Person.sum { |person| person.age } # => 4562
Person.sum(1000) { |person| person.age } # => 5562

If the relation hasn’t been loaded yet, calling sum with a block will load all records in the relation. If there are a lot of records in the relation, loading all records could result in performance issues.