so i have a database filled with stats and i need to return a number from those stats for processing. how would i go about counting how many of a certian thing there are in a particular column..
example: say i wanted to see how many records showed female in the users table but i didn't actually want to pull a bunch of info, i just want the number returned.
thanks.. i hope this makes sense.
isn't it just User.count(:conditions => {:sex => 'female'}) syntax may be a bit wrong, but you should be able to google to sort it out.
Simon
Use the count method: Person.count("gender", :conditions=>["gender=?", "female"])
There are more calculation methods available in the ActiveRecord Calculations model if you check the documentation.
-Matt
Hi there Morgan,
Something such as the following should do the trick: Article.count(:conditions => "status = 'active'")
HTH, Schalk
Morgan Morgan wrote:
Count operates using three different approaches.
* Count all: By not passing any parameters to count, it will return a count of all the rows for the model. * Count using column: By passing a column name to count, it will return a count of all the rows for the model with supplied column present * Count using options will find the row count matched by the options used.
The third approach, count using options, accepts an option hash as the only parameter. The options are:
* :conditions: An SQL fragment like "administrator = 1" or [ "user_name = ?", username ]. See conditions in the intro to ActiveRecord::Base. * :joins: Either an SQL fragment for additional joins like "LEFT JOIN comments ON comments.post_id = id" (rarely needed) or named associations in the same form used for the :include option, which will perform an INNER JOIN on the associated table(s). If the value is a string, then the records will be returned read-only since they will have attributes that do not correspond to the table‘s columns. Pass :readonly => false to override. * :include: Named associations that should be loaded alongside using LEFT OUTER JOINs. The symbols named refer to already defined associations. When using named associations, count returns the number of DISTINCT items for the model you‘re counting. See eager loading under Associations. * :order: An SQL fragment like "created_at DESC, name" (really only used with GROUP BY calculations). * :group: An attribute name by which the result should be grouped. Uses the GROUP BY SQL-clause. * :select: By default, this is * as in SELECT * FROM, but can be changed if you, for example, want to do a join but not include the joined columns. * :distinct: Set this to true to make this a distinct calculation, such as SELECT COUNT(DISTINCT posts.id) … * :from - By default, this is the table name of the class, but can be changed to an alternate table name (or even the name of a database view).
Examples for counting all:
Person.count # returns the total count of all people
Examples for counting by column:
Person.count(:age) # returns the total count of all people whose age is present in database
Examples for count with options:
Person.count(:conditions => "age > 26") Person.count(:conditions => "age > 26 AND job.salary > 60000", :include => :job) # because of the named association, it finds the DISTINCT count using LEFT OUTER JOIN. Person.count(:conditions => "age > 26 AND job.salary > 60000", :joins => "LEFT JOIN jobs on jobs.person_id = person.id") # finds the number of rows matching the conditions and joins. Person.count('id', :conditions => "age > 26") # Performs a COUNT(id) Person.count(:all, :conditions => "age > 26") # Performs a COUNT(*) (:all is an alias for '*')
Note: Person.count(:all) will not work because it will use :all as the condition. Use Person.count instead.