Single Row Subquery Returns More Than One Row

I am trying to update a table with the following query.

UPDATE TBLEWC_TASK_INSTANCE
SET TASK_INSTANCE_ID =
(

SELECT 	A.TASK_INSTANCE_ID
FROM	      TBLTASK_INSTANCE A, TBLEWC_TASK_INSTANCE B
WHERE       A.TASK_ID IS NULL 
AND         B.TASK_INSTANCE_ID IS NULL
AND         A.EWC_INSTANCE_ID = B.EWC_INSTANCE_ID 

I keep getting the following error message: ORA-01427 Single row subquery returns more than one row.

If any one has seen this before please let me know.

Thanks!

Kevin Received on Fri Oct 19 2001 - 16:32:49 CEST