ALTER FUNCTION "DBA"."f_DosToWin"( IN str char(255) )
RETURNS CHAR(255)
DETERMINISTIC
BEGIN
    DECLARE "res" CHAR(255);
    DECLARE alfaWin CHAR(255);
    DECLARE alfaDos CHAR(255);
    DECLARE i integer;
    DECLARE c1 CHAR(1);
    DECLARE ind integer;
    DECLARE flag tinyint;
    
    SET i = 1;
    SET alfaWin = 'абвгдеёжзийклмнопрстуфхцчшщьэъюяАБВГДЕЁЖЗИЙКЛМНОПРСТУФХЦЧШЩЬЭЪЮЯ№ыЫ';
    SET alfaDos = char(160) || 'ЎўЈ¤Ґс¦§Ё©Є«¬­®ЇабвгдежзиймнкопЂЃ‚ѓ„…р†‡€‰Љ‹ЊЌЋЏђ‘’“”•–—™њќљћџьл›';

    WHILE i <= LENGTH(str) LOOP        
        SET c1 = SUBSTRING(str, i, 1);
        SET flag = 0;
        SET ind = 1;

        WHILE flag = 0 LOOP
            SET ind = LOCATE(alfaDos, c1, ind + 1);        
            IF ind = 0 or (ind > 0 and ASCII(SUBSTR(alfaDos,ind,1)) = ASCII(c1)) THEN 
                SET flag = 1;
            END IF;
        END LOOP;

        IF ind > 0 THEN SET c1 = SUBSTR(alfaWin, ind, 1) END IF;
        SET res = res||c1;        
        SET i = i + 1;
        
    END LOOP;
  
    RETURN res;
END

update table
set fio = replace(fio,char(160),'а')