Checking Function Parameter Postgres - postgresql

Question

i'm trying to find the fastest way to check whether my postgres function parameter is null or empty.
my current function looks like:
CREATE OR REPLATE FUNCTON update_seller_detail(seller_id int,
seller_name varchar, seller_address varchar, seller_gender varchar)
RETURNS character varying
LANGUAGE plpsql
SECURITY DEFINER
AS $function$
BEGIN
IF seller_id = '' THEN
RAISE NOTICE 'Check Parameter'
return -1
ELSE
IF seller_name = '' THEN
UPDATE seller SET address=seller_address, gender=seller_gender WHERE id=seller_id;
ELSEIF seller_address = '' THEN
UPDATE seller SET name=seller_name, gender=seller_gender WHERE id=seller_id;
ELSE seller_gender= '' THEN
UPDATE seller SET name=seller_name, address=seller_address WHERE id=seller_id;
END IF;
END IF;
END;
$function$
Is there any way to find which of the parameter is null? so i can set my update to the column that's not null. thanks

Answer 1

you can use coalesce(nullif(trim(<column-reference>), '') in update query with column reference:
CREATE OR REPLACE FUNCTION update_seller_detail(
seller_id int,
seller_name varchar,
seller_address varchar,
seller_gender varchar
)
RETURNS character varying
LANGUAGE plpgsql
SECURITY DEFINER
AS
$function$
BEGIN
IF seller_id ISNULL THEN
RAISE NOTICE 'Check Parameter';
return -1;
ELSE
UPDATE public.seller s
SET name = coalesce(nullif(trim(seller_name), ''), s.name),
address = coalesce(nullif(trim(seller_address), ''), s.address),
gender = coalesce(nullif(trim(seller_gender), ''), s.gender)
WHERE id = seller_id;
return 1;
END IF;
END;
$function$