Ruby on Rails - Finders


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Following are the ways to find out records with and without conditions −

The following will find an author with ID 50.

Author.find(50)

The following will find authors with ID 20, 30 and 40.

Author.find([20,30, 40])

The following will find all the authors −

Author.find :all

The following will find all the authors with first name alam.

Author.find :all
            :condition => ["first_name =?", "alam" ]

The following will find the first record of the authors with first name alam.

Author.find :first
            :condition => ["first_name =?", "alam" ]

Options for Finders

You can use following option along with find function.

  • :order => 'name DESC' Use this option to sort the result in ascending or descending order.

  • :offset => 20 Starts fetching records from offset 20.

  • :limit => 20 Returns only 20 records.

  • :group => 'name' This is equivalent to sql fragment GROUP BY.

  • :joins => LEFT JOIN ...' Additional LEFT JOIN (rarely used).

  • :include => [:account, :friends] This is LEFT OUTER JOIN with these model.

  • :select => [:name, :address] Use this instead of SELECT * FROM.

  • :readonly => true Use this to make objects write protected.

Dynamic attribute-based Finders

You can use more dynamic functions to fetch values.

If there is a field user_name, then you can use the following to find records by user name.

Person.find_by_user_name(user_name)

If there is a field last_name, then you can use the following to find records by last name.

Person.find_all_by_last_name(last_name)

If there are fields user_name and password, then you can use the following to find a record for a given user name and password.

Person.find_by_user_name_and_password(user_name, password)

rails-references-guide.htm

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