row1:1,2,3,4,5,6
row2:1,2,3,4,5,6

col1   col2
=====  ====
1       3
1       3

col1   col2   col3
=====  ====   ====
1       3       5
1       3       5

load data
infile *
insert into table T1 fields terminated by ',' TRAILING NULLCOLS
(col1,fill1 filler,col2)
insert into table T2 fields terminated by ',' TRAILING NULLCOLS
(col1,fill2 filler,col2,fill3 filler,col3)
begindata
1,2,3,4,5,6
1,2,3,4,5,6

load data
    infile *
    truncate
    into table T1
    fields terminated by ',' trailing nullcols
    ( col1
    , fill1 filler
    , col2  )
    into table T2
    fields terminated by ','  trailing nullcols
    ( col1 position(1)
    , filler filler
    , col2
    , filler2 filler
    , col3 )

BEGINDATA
1,2,3,4,5,6
1,2,3,4,5,6

SQL> select * From t1;

      COL1       COL2
---------- ----------
         1          3
         1          3

SQL> select* From t2;

      COL1       COL2       COL3
---------- ---------- ----------
         1          3          5
         1          3          5

LOAD DATA
INFILE *
INSERT INTO TABLE T1 FIELDS TERMINATED BY ',' TRAILING NULLCOLS
(COL1, FILL2 FILLER, COL2, FILL4 FILLER, FILL5 FILLER, FILL6 FILLER)
INSERT INTO TABLE T2 FIELDS TERMINATED BY ',' TRAILING NULLCOLS
(COL1, FILL2 FILLER, COL2, FILL3 FILLER, COL3, FILL6 FILLER)
BEGINDATA
1,2,3,4,5,6
1,2,3,4,5,6