Help : Update and insert record based on several value in the parameter

Hi,

I want to create a function to update my table (flag='9') and insert new
record (flag='0') with the rfidnumber specified in a parameter.

This parameter may have several value seperated by space (ie. 11 22 33 44)

CREATE OR REPLACE FUNCTION public.fcreate_rfid (
znumber varchar
)
RETURNS boolean AS
$body$
BEGIN
--update old record which has the same rfid number and flag='0' if exists
update tblrfid set flag='9' where flag='0' and rfidnumber in (znumber);

-- generate new record
insert into tblrfid(tanggal, flag, rfidnumber)
select localtimestamp, '0', regexp_split_to_table(znumber, ' ');

return true;
END;
$body$
LANGUAGE 'plpgsql';

when i called this function using command :

select fcreate_rfid('11 22 33 44');

This function fail to update the old record, but success to insert the new
record.

Please help me how to fixed this problem. I know the problem is the update
command, but i don't know the correct it. Googling anywhere didn't find a
solution.

Thank you

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