Internal table

Hello Gurus,

I have uploaded a text file into an internal table.My txt file contains 4 fileds tab delimited.After i uploaded my internal table looks like this

A -

B--

D

-

1--

2-

3----

4

4--

-

6----

Now what my requirement is i want only rows in such a way that at any time for each row there shud only one field 2 be populated. and others are to b deleted.

In the above case i shud have only rows 2,4,5 and rest to be deleted from the internal table.

Thanks in advance

How can i achieve this?