JOIN error

Hi all, I have written the following join:

DATA:

IT_WRKGDATES TYPE STANDARD TABLE OF EINDT.

DATA:

WA_WRKGDATES TYPE EINDT.

SELECT EINDT MENGE

INTO CORRESPONDING FIELDS OF TABLE IT_RELEASE

FROM

EKEK AS A

JOIN EKEH AS B

ON

A_{EBELN = B}EBELN AND

A_{EBELP = B}EBELP AND

A_{ABART = B}ABART AND

A_{ABRUF = B}ABRUF

WHERE

A~EBELN = WA_PURDOC-EBELN AND

A~EBELP = WA_PURDOC-EBELP AND

A~ABART = '2' AND

B~EINDT IN IT_WRKGDATES.

I needed to run this query for all records in the internal table IT_WRKGDATES...but the system gives the error "The line structure of the table IT_WRKGDATES is incorrect"..

Can anybody suggest what the problem might be?