Substract two field values to insert the result into a third value

[josjorge]

Hi,

I have this question, having two numeric values field1 and field2, i need field3 by default to be the difference between field1 and field , any idea??

[Kruptein]

in one query:

UPDATE table SET field3 = field1-field2

I think this should work.

(everytime you update/change a value of field1/field2 you will have to do this query, mysql can't do this automatic..)

[SKANK!!!!!]

or you can like be all cool and be like well find the column names and then do it with php $column1 - $ column2