Function is not working with varchar records

I have a function that in theory will give the country name as output when the input is the city name:

CREATE OR REPLACE FUNCTION public.country_by_city(city varchar, OUT Country varchar)  
RETURNS varchar  
LANGUAGE SQL AS 
$function$   
    SELECT c.country     
    FROM country c   
    JOIN city c2 ON c2.country_id = c.country_id     
    WHERE c2.city = $1   
$function$ 
; 

And it’s working if I will change c2.city to c2.city_id but when I am trying to call a function with a varchar column in it, for example :

SELECT public.country_by_city(Abha);

I get this error:

SQL Error [42703]: ERROR: column "abha" does not exist

I tried to use UPPER() or INITCAP(), and it didn’t help. It’s worth mentioning that city name records in the city table have capitalized first letters.

>Solution :

You need to call this parameter using simple quotes, for example:

SELECT public.country_by_city('Abha');