Rails find record with zero has_many records associated
102109
Want to find records with no associated records in Rails
98058
Ordered associations
16054
Return not exists record in the table
86687
Django: How to select a limited amount of rows for each foreign key?
45766
What is scope/named_scope in rails?
134117
Defining foreign key relationships for Rails' models
128698
Losing an Attribute When Saving Through an Association w/ Scope (Rails 4.0.0)
2913
Find records from one table which don't exist in another
72720
How to skip ActiveRecord callbacks?
116700
Can I or SHOULD I find an object by the object_id attribute in ruby?
10138
How to avoid NoMethodError for missing elements in nested hashes, without repeated nil checks?
91428
GroupBy a list of associations with their keys
6011
How do I build a SOQL query for records in a list of IDs?
54977
Many to Many and Weak Entities
70775
Rails: How can I set default values in ActiveRecord?
30674
get record with at least one associated object
148325
What's the difference between belongs_to and has_one?