MySQL Insert Where query

Question

What\'s wrong with this query:

INSERT INTO Users( weight, desiredWeight ) VALUES ( 160, 145 ) WHERE id = 1;

It works without the WHE

Answer 1

INSERT INTO Users(weight, desiredWeight )
SELECT '$userWeight', '$userDesiredWeight'  
FROM (select 1 a ) dummy
WHERE '$userWeight' != '' AND '$userDesiredWeight'!='';