Validace IČ

Vycházím z algoritmu publikovaného na http://latrine.dgx.cz/jak-overit-platne-ic-a-rodne-cislo.

CREATE OR REPLACE FUNCTION validate_ic(varchar)
RETURNS boolean AS $$
DECLARE 
  s integer;
  str_parts varchar[];
BEGIN
  SELECT INTO str_parts regexp_matches 
     FROM regexp_matches($1, E'^(\\d{8})$');
  IF FOUND THEN 
    s := (SELECT sum(to_number(substring($1 FROM i FOR 1),'9') * v) % 11 
             FROM (values(1, 8),(2,7),(3,6), (4,5),(5,4),(6,3), (7,2)) g(i,v));
    RETURN CASE WHEN s IN (0,10) THEN substring($1 FROM 8 FOR 1) = '1'
                WHEN s = 1 THEN substring($1 FROM 8 FOR 1) = '0'
                ELSE to_number(substring($1 FROM 8 FOR 1), '9') = 11 - s END;
  ELSE
    RETURN false;
  END IF;
END;
$$ LANGUAGE plpgsql IMMUTABLE STRICT;

Výsledek ověříme:

postgres=# select validate_ic('69663963');
 validate_ic 
-------------
 t
(1 row)