Sql query for update and inner join

Hi,
I have a inner join sql query to get startDate from table Personal_details and EndDate from table'CU_CABLES_PRES_PEN_DETAIL'

The requirement is to have start date one day after end date.If a null Date is found for end date I need to insert the value in it.


How can I create a query to achieve this

Query inner join:

SELECT a.refno, a.DATELEFT as dateleft , b.CU_CABPPD_StartDate as startDate FROM PERSONAL_DETAILS as a INNER JOIN CU_CABLES_PRES_PEN_DETAIL as  b  ON a.REFNO = b.refno

The data current has some null end dates which need to be filled in appropriately.
Some records where end date is equal to startdate
Some records where end date is after startdate


Many thanks in advance

Cheers


Refno       StartDate                      EndDate
10001      01/08/2005 00:00      NULL
10008      01/08/2005 00:00      NULL
10009      12/11/2001 00:00      11/11/2001 00:00
10010      18/08/2001 00:00      17/08/2001 00:00
10015      01/08/2005 00:00      NULL
10017      01/02/2002 00:00      31/01/2002 00:00
10018      01/08/2005 00:00      31/07/2005 00:00
10020      01/11/2002 00:00      31/10/2002 00:00
10021      05/02/2001 00:00      04/02/2001 00:00
10022      06/02/2001 00:00      06/02/2001 00:00
10023      07/02/2001 00:00      08/02/2001 00:00