Postgres function parameter is null then replace it with default value

Question

I have a postgres function

 create or replace function start_batch(in start_date date, int end_date date) returns integer 
as $batch$

BEGIN
    
    if(start_date is null or end_date is null) then
           start_date = date_trunc('month',now())-interval '1 month')::date ;
            end_date = date_trunc('month'now())-interval '1 day')::date;
        end if;
    
    
END;
$bach$ language plpgsql;

but i get syntax error SQL errir [42704] ERROR: unrecognized exception condition "is null" is there any other way to check if in parameter date is null and replace it with default date

Answer 1

You have many incorrect syntaxes here.

Sample for you, this is working:

CREATE OR REPLACE FUNCTION test(start_date date)
 RETURNS date
 LANGUAGE plpgsql
AS $function$
begin
    
    if (start_date is null) then 
    start_date = date_trunc('month', now() - interval '1 month')::date;
    end if; 

    return start_date;
    
end ;
$function$
;

select test(null)

-- Result: 
2022-11-01