Runtime error ITAB_DUPLICATE_KEY due to declaration of internal table type hashed table

Hi All,

I am facing runtime error  ITAB_DUPLICATE_KEY during retreving the data from the VBKD table into an internal table type hashed table.

Actually I am performing the following things..

Firstly I am retreving the data from the custom table into a internal table which is declared as TYPE STANDARD TABLE WITH DEFAULT KEY.

Upto this is fine..

Again retreving the data from the VBKD table for all entries in the above internal table into an another internal table which is declared as

TYPE HASHED TABLE WITH UNIQUE KEY VBELN.

I am getting runtime error as ITAB_DUPLICATE_KEY.

Whether is there any problem in the declaration of the second internal table?

And also for the VBKD table as I observe that there are 2 KEY fields which are VBELN and POSNR.

If the table contains 2 key fields, then whether can we declare the internal table like hashed table with unique key as 1 field  i.e VBELN?

Whether runtime error is due to the Declaration...?

I know if we declare the internal table as NON-UNIQUE KEY then runtime error wont occurs..

But I need to know whether I am declaring the internal tabel correctly i.e if there are 2 key fields can we declare unique key with 1 key field...If YES...then what was the reason for the runtime error.

Any suggestion will be appreciated.

Regards

Raj