SQLite Forum

Help with foreign key
BTW, your description is confusing.

The terminology for a relationship between two tables in a Relational Database is a Parent-Child relationship.  One table has a column(s) which is the "parent" of the relationship, and another (or the same) table contains a column(s) which is the "child".  

A "child" has exactly one "parent" (which may be NULL, as in unknown), and a "parent" may have 0 to N "child"s. 

The "REFERENCES" constraint is a constraint on the child table column(s) and points to (references) what constitutes the parent or the relationship.  

The relationship is *ALWAYS* 1 to N between parent and child -- the parent column(s) must be a unique key or primary key (candidate key).  The child column(s) should have an index on them for performance reasons.  If the child columns are constrained UNIQUE then the parent:child relationship 1:N has N limited to being 0 or 1.  If the child column(s) are NULL then that child has no parent.