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I know I've seen this before but I can't find anything now. I want to group a query by a certain column and be able to display how many are in each group. I got the first part down:
@line_items = @project.line_items.all(:group => "device_id") This is for my line item index view, which is just a table displaying the line items. How do I make a column in that table for "count" now that the line items are grouped by device?
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SQL COUNT( ) with group by and order byThe GROUP BY makes the result set in summary rows by the value of one or more columns. Each same value on the specific column will be treated as an individual group.
The group_by() of enumerable is an inbuilt method in Ruby returns an hash where the groups are collectively kept as the result of the block after grouping them. In case no block is given, then an enumerator is returned.
Active Record is the M in MVC - the model - which is the layer of the system responsible for representing business data and logic. Active Record facilitates the creation and use of business objects whose data requires persistent storage to a database.
You can do count on line_items which will return you an ordered hash of device_id and count.
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