Connected to:
Oracle9i Enterprise Edition Release 9.2.0.8.0 - 64bit Production
With the Partitioning, OLAP and Oracle Data Mining options
JServer Release 9.2.0.8.0 - Production

SQL> create table test(sold_to varchar2(10));

Table created.

SQL> create or replace trigger trg before insert on test
  2  for each row
  3  begin
  4  :NEW.SOLD_TO  := trim(:NEW.SOLD_TO);                                       
  5  END;
  6  /

Trigger created.

SQL> desc pie
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 SOLD_TO                                            VARCHAR2(12)

SQL> insert into test select * from pie;
insert into test select * from pie
                        *
ERROR at line 1:
ORA-01401: inserted value too large for column


SQL> insert into test select trim(sold_to) from pie;

105107 rows created.

SQL>