Using Procedural Language PostgreSQL for a Fibonacci number implementation.

fibonacci.sql

-- Trying a fibonacci on pl/pgsql

create or replace function fibonacci( step integer )
    returns integer as
    $$
    begin
        -- raise info 'step %', step;
        if step = 0 then
            return 0;
        else
            if step = 1 then
                return 1;
            else 
                return fibonacci( step := step - 1 ) + fibonacci( step := step - 2 );
            end if;
        end if; 
    end;
    $$
    language plpgsql;
    
-- Test it:
-- select fibonacci(10);  -- 55