An SQL statement for Mysql database required

Two mysql tables: Part, Part Association Part attributes: id, name, type Part Association attributes: child_part_id, parent_part_id (i.e. Part has two one-to-many relationships with Part Association) Sample values:- Part: [id, type] 1,A; 2,A; 3,A; 4,A; 5,A; 6,B; 7,B; 8,B; 9,C; 10,C; 11,D. Part Association: [child_part_id, parent_part_id] 1,6; 2,9; 3,6; 3,9; 4,7; 5,11; 7,9; 10,1; 10,5. I want sql to return all parts which are of a specific type ($firsttype) but which are not related to another part which is of another specified type ($secondtype). Example (1), for: $firsttype='A', $secondtype='B' Result should be Part id's: 2, 5. That is parts 2 and 5 are of type 'A' but are not related to any part of type B. Example (2), for: $firsttype='A', $secondtype='C' Result should be Part id's: 1, 4, 5. That is parts 1, 4 and 5 are of type 'A' but are not related to any part of type C. Example (3), for: $firsttype='B', $secondtype='C' Result should be Part id's: 6, 8. That is parts 6 and 8 are of type 'B' but are not related to any part of type C.