Bidirectional relationships in ActiveRecord
41821
How do I do reflexive self-join relationships in ActiveRecord?
108559
How to stack three relations
130249
Performing relate in ModelBuilder for one to many relationship?
141930
Implementing a "Both, Either-or, but Not Null" Requirement in a Database
66985
Is there a name for this database schema of key values?
30986
Combine two ActiveRecord::Relation objects
84126
Database design - many-to-many relationship between three columns
18521
One-to-many joins in QGIS
126524
How to identify look up relations to an object in Salesforce
132926
Bidirectional Map
148325
What's the difference between belongs_to and has_one?
45949
Is there a simpler way of drawing relation maps?
41165
Foreign key constraints failures
69500
How do I add migration with multiple references to the same model in one table? Ruby/Rails
149602
One to at most one relation or multiple null columns?
77391
How to implement a super class, sub class relationship in the database?
75985
Given the functional dependencies of a relation is there more then one way to normalize it?