Re: Update a field in a file from the trigger on the same file

On 30-May-2014 11:06 -0500, Luis Rodriguez wrote:

On 30-May-2014 10:15 -0500, Jeff Young wrote:

I have a file that I want to monitor for a change to a specific
field. If this field becomes negative, I want to set it to zero.
<<SNIP>>

<<SNIP>>

A SQL trigger would be very simple. Something like:

create trigger mylib/mytrig
before update on mylib/myfile
referencing new as new_row
for each row mode db2row
begin
if new_row.myfield< 0
set new_row.myfield = 0
endif;
END;

Given the scenario as described, and better for performance because the trigger is not invoked unless the I/O request includes the "specific field" as an updated column, a small variation on that SQL TRIGGER [using *BEFORE UPDATE OF*]:

create trigger mylib/mytrig
before update of the_specific_field /* <-- addendum */
on mylib/myfile
referencing new as new_row
for each row mode db2row
begin
if new_row.myfield < 0
set new_row.myfield = 0
endif;
end /* FWiW: officially, there is no semicolon here */