Counting Associated Records from MySQL Result

Rails
1

Hey All,

I’m currently working on a Guitar Reviews website and I think i’ve been
coding for way to long and forgot the basics…I’m having trouble doing a
simple SQL method.

I have 2 Tables, 1 for Guitar Manufacturers (gmanufacturers) and 1 for
Guitar Models (gmodels), every model has a manufacturer and every
manufacturer has many models (gmodel belongs_to :gmanufacturer &
gmanufacturer has_many :gmodels). What i’m trying to do is; when I list
all of the gmanufacturers, I want to show how many models each
manufacturer has, ex:

Manufacturer 1
[ 2 Models ]

Manufacturer 2
[ 15 Models ]

etc…

So, I assume I would have to loop the result of a Gmanufacturer.find
:all into a Gmodel.count statement, but havent been able to come up with
anything.

Forgive me if this is a bit too confusing…just reply and i’ll explain
better.

Thanks!

2

Eric,

You should be able to do a loop over all manufacturers and put each
into a manufacturer variable. Then:

[ <%= gmanufacturer.gmodels.count %> Models ]

should give you the result you are looking for. If you add an :include
=> [:gmodels] to your find then you will get the results with only one
call to the database. Here is a full example:

@gmanufacturers = GManufacturers.find(:all, :include =>[:gmodels])

3

Carl F. wrote:

Eric,

You should be able to do a loop over all manufacturers and put each
into a manufacturer variable. Then:

[ <%= gmanufacturer.gmodels.count %> Models ]

should give you the result you are looking for. If you add an :include
=> [:gmodels] to your find then you will get the results with only one
call to the database. Here is a full example:

@gmanufacturers = GManufacturers.find(:all, :include =>[:gmodels])

Thanks Carl. That worked perfectly. Except, I came up with another
annoying feature I might need…

Would it be possible to define a condition for the count? like, where
approved = ‘true’?

Thanks,

  • Eric
4

Try something like,

gmanufacturer.gmodels.find(:all, :conditions => “approved = ‘true’”)

5

If you are looking for approved manufacturers:

@gmanufacturers = GManufacturers.find(:all, :include => [:gmodels],
:conditions => [“approved = ‘true’”])

If you are looking for approved models:

@gmanufacturers = GManufacturers.find(:all, :include => [:gmodels],
:conditions => [“gmodels.approved = ‘true’”])

Check out the docs for find. They are pretty good.