SELECT *
  FROM FK_Table
 WHERE ForeignKey NOT IN (SELECT PrimaryKey FROM PK_Table);


This works as written for single-column keys.  It can also work for multi-column keys if your DBMS allows the notation:

SELECT *
  FROM FK_Table
 WHERE (FK_Col1, FK_Col2) NOT IN (SELECT PK_Col1, PK_Col2 FROM PK_Table);


Not every DBMS supports this, though.  This formulation with NOT EXISTS should work most places:

SELECT *
  FROM FK_Table
 WHERE NOT EXISTS (SELECT 1
                     FROM PK_Table
                     WHERE FK_Col1 = PK_Col1 AND FK_Col2 = PK_Col2
                  );


Finding columns that do not match existing primary key
How does the colour of ambient lighting affect colour rendition?

For example:

If I stand under a sodium-vapour (orange) streetlight and calibrate my camera's white balance, what effect would this have if I were to take a photo of a colour test chart?  Presumably, white would still render as white due to the white balance calibration, but how would other colours be rendered?

How would the result differ under primary and secondary coloured lighting, e.g. a red or yellow light?

Thanks.
