Add/subtract from a database value

[Anonymous Monk]

I need help doing some basic arithmatic on some database values. Initially, I query my table for all product codes and quantity ( using DBI ). Then I display these non-editable values along with two editable fields for entering a value that will be added/subtracted from original quantity in a form (using CGI) so it looks something like this:

Product Name  |  Quantity  |  Add  |  Subtract

WidgetA       |  10        |       |
.
.
.

What I need to do happen when the form is submitted is take all the input in the add and/or subtract fields and do the appropriate math on the original quantity value, then store the newly calculated quantity back into the table. Can anyone please give me a good example to work with?

[Abigail]

Eh, what piece do you have problems with? Everything seems trivial to me. Use an SQL statement to retrieve the values from the table. Use print to print out the form. Use CGI to parse the form response. Use + and - to add or subtract values, and use another SQL query to store the results.

-- Abigail

[LeGo]

Would something like this help? Just use those commands and adapt.

$dbh = DBI->connect( "dbi:mysql:user", "webserver", "pwd") or dienice(
+"Can't connect: ",$dbh->errstr);
my $sub = param("sub");
my $add = param("add");
if($add){
   $sth = $dbh->do("update database set count=count+$add where address
+=\"$whatever\"")
}
if($sub){
   $sth = $dbh->do("update database set count=count-$sub where address
+=\"$whatever\"")
}

Feel free to update this or correct this as this is the way I do things and if there is a better way or something that I am missing please do let me know.

LeGo

[Anonymous Monk]

If Im naming my "Add" and "Sub" fields like this:

while ( my $fieldnames = $db->fetchrow_hashref ) {
      #append product code to "add_" so all text fields
      #are named "add_WidgetA" and so forth
}

how do I go about getting every value and then adding to the appropriate field?