We had a requirement to validate non-english characters in the data.
Well, i used standard function regexp_like(column, '[A-Z]') considering those characters which are not replaced by this function are non-english, to my surprise it is not considering turkish characters.
select REGEXP_replace(UPPER('rn Aıklaması'), '[A-Z]','')Test from dual ;
Alternate Solution for this problem is using : asciistr Function
If input is equal to asciistr function, then it is non-english.
select count(*) from dual where 'ĞEĞİK' <> asciistr('ĞEĞİK') ;