Rails - Mar 2006 - Running total of a field in child records

What is the best way to get the running total of a number field in child
records. Let say I have an Order model, which has_many :line_items, and each
LineItem has an amount field. I would like to get the grand total of a
specific Order. Is it a good idea to add a ''total'' column in
the ''orders''
table and update it every time a line_item is created/updated/deleted?
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http://wiki.rubyonrails.org/rails/pages/MagicFieldNames

see Counter Cache section as one of the solutions

On 3/20/06, Jong Hian Zin <mail.zin@gmail.com>
wrote:
>
> What is the best way to get the running total of a number field in child
> records. Let say I have an Order model, which has_many :line_items, and
each
> LineItem has an amount field. I would like to get the grand total of a
> specific Order. Is it a good idea to add a ''total'' column
in the ''orders''
> table and update it every time a line_item is created/updated/deleted?
>
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
>
>
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