PL/SQL. Parse clob UTF8 chars with regexp_like regular expressions - regex

Question

I want to check if any line of my clob have strange characters like (ñ§). These characters are read from a csv-file with an unexpected encoding (UTF-8) which converts some of them.
I tried to filter each line using a regular expression but it's not working as intended. Is there a way to know the encoding of a csv-file when read?
How could I fix the regular expression to allow lines with only these characters? a-zA-Z 0-9 .,;:"'()-_& space tab.
Clob example readed from csv:
l_clob clob :='
"exp","objc","objc","OBR","031110-5","S","EXAMPLE","NAME","08/03/2018",,"122","3","12,45"
"xp","objc","obj","OBR","031300-5","S","EXAMPLE","NAME","08/03/2018",,"0","0","0"
';
Another clob:
DECLARE
l_clob CLOB
:= '"exp","objc","objc","OBR","031110-5","S","EXAMPLE","NAME","08/03/2018",,"122","3","12,45"
"xp","objc","obj","OBR","031300-5","S","EXAMPLE","NAME","08/03/2018",,"0","0","0"';
l_offset PLS_INTEGER := 1;
l_line VARCHAR2 (32767);
csvregexp CONSTANT VARCHAR2 (1000)
:= '^([''"]+[-&\s(a-z0-9)]*[''"]+[,:;\t\s]?)?[''"]+[-&\s(a-z0-9)]*[''"]+' ;
l_total_length PLS_INTEGER := LENGTH (l_clob);
l_line_length PLS_INTEGER;
BEGIN
WHILE l_offset <= l_total_length
LOOP
l_line_length := INSTR (l_clob, CHR (10), l_offset) - l_offset;
IF l_line_length < 0
THEN
l_line_length := l_total_length + 1 - l_offset;
END IF;
l_line := SUBSTR (l_clob, l_offset, l_line_length);
IF REGEXP_LIKE (l_line, csvregexp, 'i')
THEN -- i (case insensitive matches)
DBMS_OUTPUT.put_line ('Ok');
DBMS_OUTPUT.put_line (l_line);
ELSE
DBMS_OUTPUT.put_line ('Error');
DBMS_OUTPUT.put_line (l_line);
END IF;
l_offset := l_offset + l_line_length + 1;
END LOOP;
END;

Answer 1

If you only want to allow special characters you can use this regex:
Your Regex
csvregexp CONSTANT VARCHAR2 (1000) := '^[a-zA-Z 0-9 .,;:"''()-_&]+$' ;
Regex-Details
^ Start of your string - no chars before this - prevents partial match
[] a set of allowed chars
[]+ a set of allowed chars. Has to be one char minimum up to inf. (* instead of + would mean 0-inf.)
[a-zA-Z]+ 1 to inf. letters
[a-zA-Z0-9]+ 1 to inf. letters and numbers
$ end of your string - no chars behind this - prevents partial match
I think you can work it out with this ;-)
If you know there could be an other encoding in your input, you could try to convert and check against the regex again.
Example-convert
select convert('täst','us7ascii', 'utf8') from dual;