Strange foreign key behavior on empty tables in SQLite 3

Question

I have SQLite 3 with the following setup (simplified):

create table Location(LocationId integer not null,
                      LocationCode text not null, 
             


        

Answer 1

The documentation (hidden in the source code) says:

A foreign key constraint requires that the key columns in the parent table are collectively subject to a UNIQUE or PRIMARY KEY constraint. […] If the required index cannot be found, either because:

1. The named parent key columns do not exist, or
2. The named parent key columns do exist, but are not subject to a UNIQUE or PRIMARY KEY constraint, or
3. No parent key columns were provided explicitly as part of the foreign key definition, and the parent table does not have a PRIMARY KEY, or
4. No parent key columns were provided explicitly as part of the foreign key definition, and the PRIMARY KEY of the parent table consists of a a different number of columns to the child key in the child table.

then … a "foreign key mismatch" error [is raised].

> DELETE FROM Child;
Error: foreign key mismatch
> CREATE UNIQUE INDEX di ON Department(DepartmentId);
> DELETE FROM Child;
>