Simple MySQL query question

[Maracles]

I have a form for updating certain records in my database, when the form is submitted I am using UPDATE to replace the relevant corresponding fields in the database.

 

My problem is that my query tries to update all fields therefore if the user has left a field blank in fields that don't need to be changed, when they click submit the query will update those fields with 0 regardless. How do I write my query so that UPDATE only works on fields that have data in them?

 

My query is below:

$query = "UPDATE gross SET day1 = '$daynew1', day2 = '$daynew2', day3 = '$daynew3', day4 = '$daynew4', day5 = '$daynew5', day6 = '$daynew6', day7 = '$daynew7' where filmID = '$filmID'";

 

i.e. if a user changes the value of day1 then I want this to update however if they have not changed day2 I don't want this to update.

 

Thanks for any help.

 

[fenway]

That's up to your script to determine.