Postgresql function with if statement

Question

How can I make this pseudo code to work in Postgresql:

create or replace function getf(arg character varying(255)) returns int
as $$
if arg = 'a' then return 1;
else return 2;
$$ language sql;

Based on argument I need to return some values and there is no other table I need to query. Just need to build a logic inside function. Tried to replace if with when clause, but could not figure out how to do it.

Thanks!

Answer 1

create or replace function getf(arg character varying(255)) returns int as $$
begin
  if arg = 'a' then
    return 1;
  else 
    return 2;
  end if;
end; $$ language plpgsql;

Note that this is a PL/pgSQL function.

The online manual has an excellent chapter on PL/pgSQL. That should provide everything you need to get started writing procedural function with ample support for logical branching.

Answer 2

Using sql language, you can do it using case when:

create or replace function getf(arg character varying(255)) returns int as
 $$

select case 
        when arg = 'a' 
         then 1
         else 2 
       end

$$ language sql;