PL SQL Data Types Oracle PLSQL Tutorial

Remove characters from a string.
LTRIM does it from the left side of the string
PTRIM does from the right side.
TRIM does it from the both side.

SQL>
SQL> declare
  2      v1_tx VARCHAR2(20):='Hello!';
  3      v2_tx VARCHAR2(20);
  4      v3_tx VARCHAR2(20);
  5  begin
  6      v3_tx:= trim (both '*' from v2_tx);
  7      DBMS_OUTPUT.put_line(v3_tx);
  8      v3_tx:= trim (leading '*' from v2_tx);
  9      DBMS_OUTPUT.put_line(v3_tx);
 10      v3_tx:= trim (trailing '*' from v2_tx);
 11      DBMS_OUTPUT.put_line(v3_tx);
 12  end;
 13  /
PL/SQL procedure successfully completed.
SQL>