What\'s wrong with this query:
INSERT INTO Users( weight, desiredWeight ) VALUES ( 160, 145 ) WHERE id = 1;
It works without the WHE
WHE
The simplest way is to use IF to violate your a key constraint. This only works for INSERT IGNORE but will allow you to use constraint in a INSERT.
INSERT INTO Test (id, name) VALUES (IF(1!=0,NULL,1),'Test');