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Ruby on Rails - Finders
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)
