sqlldr does not recognize empty tab delimited columns - sql-loader

Question

I am seeing a strange problem when loading my data with sqlldr. Here is my table schema:
CREATE TABLE TEST(
"COL1" VARCHAR2 (255 BYTE),
"COL2" VARCHAR2 (255 BYTE),
"COL3" NUMBER,
"COL4" VARCHAR2 (255 BYTE)
and here is just one row of data I am trying to ingest from the tab delimited file test.txt:
COL1 COL2 COL3 COL4
10 17-cc
notice that the first two columns are empty (null). So my row is really:
\t\t10\t17-cc
my loader script:
load data
infile 'test.txt'
append into table TEST
fields terminated by "\t" optionally enclosed by '"'
TRAILING NULLCOLS
(COL1,COL2,COL3,COL4)
This will be loaded into my table as:
COL1 COL2 COL3 COL4
10 17-CC (null) (null)
which is incorrect. it seems that the two leading tabs in the data row were ignored and COL3 position (10) was assigned to COL1. However, if I try to import the data as a comma separated file:
COL1,COL2,COL3,COL4
,,10,17-cc
it works as expected. Why does the tab delimited version fails here?

Answer 1

NOTE - Fixed my original wrong answer.
Your TAB is defined just fine. You need the NULLIF statement:
load data
infile 'test.txt'
append into table TEST
fields terminated by "\t" optionally enclosed by '"'
TRAILING NULLCOLS
(COL1 NULLIF(COL1=BLANKS),
COL2 NULLIF(COL2=BLANKS),
COL3 NULLIF(COL3=BLANKS),
COL4 NULLIF(COL4=BLANKS)
)