.group不返回所有列

Question

I have a .group query that is not returning all the columns in the select and I was wondering if someone could validate my syntax. Here is a query with a .group and the result from my console;

Expense.select('account_number, SUM(credit_amount)').group(:account_number).first
Expense Load (548.8ms)  EXEC sp_executesql N'SELECT TOP (1) account_number, SUM(credit_amount) FROM [expenses] GROUP BY account_number'
       (36.9ms)  SELECT table_name FROM information_schema.views

Even though I select two columns, I'm only getting the first one to return. I'm wondering if I may be dealing with an db adapter problem.

Answer 1

Try giving your sum an alias:

expense = Expense.select('account_number, SUM(credit_amount) AS credit_amount').group(:account_number).first
puts expense.credit_amount

ActiveRecord doesn't create a default alias for aggregation operations such as SUM , COUNT etc... you have to do it explicitly to be able to access the results, as shown above.

Answer 2

The SUM(credit_amount) column from the SQL has no alias and will not have a column name by default. If you change it to have an alias SUM(credit_amount) As 'A' for example and select the alias name, it should pick it up.