CREATE TABLE XT_TEST(
                     col1 number,
                      col3 varchar2(10)
                    )
  ORGANIZATION EXTERNAL(
                        TYPE ORACLE_LOADER
                        DEFAULT DIRECTORY TEMP
                        ACCESS PARAMETERS(
                                          FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
                                          MISSING FIELD VALUES ARE NULL
                                          (
                                           col1,
                                           skip_this_column char(40000),
                                           col3
                                          )
                                         )
                        LOCATION(
                                 'ext_test.txt'
                                )
                       )
/
SELECT * FROM XT_TEST
/

DROP TABLE XT_TEST
/
CREATE TABLE XT_TEST(
                     col1 number,
                     col2 varchar2(34),
                     col3 varchar2(10)
                    )
  ORGANIZATION EXTERNAL(
                        TYPE ORACLE_LOADER
                        DEFAULT DIRECTORY TEMP
                        ACCESS PARAMETERS(
                                          FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
                                          MISSING FIELD VALUES ARE NULL
                                          (
                                           col1,
                                           very_long_column char(40000),
                                           col3
                                          )
                                          COLUMN TRANSFORMS(
                                                            col2 FROM STARTOF very_long_column(34)
                                                           )
                                         )
                        LOCATION(
                                 'ext_test.txt'
                                )
                       )
/
SELECT * FROM XT_TEST
/

      COL1 COL2                               COL3
---------- ---------------------------------- ----------
         1 FIRST 34 CHARS OF VERY LONG STRING ABC

SQL>

SQL> SELECT  BANNER
  2    FROM  V$VERSION
  3  /

BANNER
--------------------------------------------------------------------------------
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
PL/SQL Release 12.2.0.1.0 - Production
CORE    12.2.0.1.0      Production
TNS for 64-bit Windows: Version 12.2.0.1.0 - Production
NLSRTL Version 12.2.0.1.0 - Production

SQL> CREATE TABLE XT_TEST(
  2                       col1 number,
  3                       very_long_column clob,
  4                       col3 varchar2(10)
  5                      )
  6    ORGANIZATION EXTERNAL(
  7                          TYPE ORACLE_LOADER
  8                          DEFAULT DIRECTORY TEMP
  9                          ACCESS PARAMETERS(
 10                                            FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
 11                                            MISSING FIELD VALUES ARE NULL
 12                                            (
 13                                             col1,
 14                                             very_long_column char(200000),
 15                                             col3
 16                                            )
 17                                           )
 18                          LOCATION(
 19                                   'ext_test.txt'
 20                                  )
 21                         )
 22  /

Table created.

SQL> SELECT  X.*,
  2          LENGTH(VERY_LONG_COLUMN) L
  3    FROM  XT_TEST X
  4  /

COL1 VERY_LONG_COLUMN                                                                 COL3          L
---- -------------------------------------------------------------------------------- ---- ----------
   1 FIRST 34 CHARS OF VERY LONG STRINGXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX ABC      131646

SQL>

SQL> SELECT  X.*,
  2          LENGTH(VERY_LONG_COLUMN) L
  3    FROM  XT_TEST X
  4  /

ERROR:
ORA-29913: error in executing ODCIEXTTABLEFETCH callout
ORA-29400: data cartridge error
KUP-04020: found record longer than buffer size supported, 524288, in C:\TEMP\ext_test.txt (offset=0)



no rows selected

SQL>