Question

Can I do something like this in SQL LOADER?

LOAD DATA
INFILE 'table_with_one_million_rows.dat'
INTO TABLE TABLE_WITH_ONE_MILLION_ROWS
FIELDS TERMINATED BY ','
TRAILING NULLCOLS
(
   COL1                     DECIMAL 
 , COL2                     DECIMAL IF COL1='X' '1' else '0'
 , COL3                     CHAR 

)

Answer 1

A condition in SQL*Loader can be performed using decode.

Using a DECIMAL in your example will get the error:

SQL*Loader-402: Unable to determine length of column COL1 from specification

Suggest using DECIMAL EXTERNAL instead:

LOAD DATA
INFILE 'table_with_one_million_rows.dat'
INTO TABLE TABLE_WITH_ONE_MILLION_ROWS
FIELDS TERMINATED BY ','
TRAILING NULLCOLS
(
   COL1                     DECIMAL EXTERNAL
 , COL2                     DECIMAL EXTERNAL "decode(:COL2, 'X', '1', '0')"
 , COL3                     CHAR 

)