Re: Single Row Subquery Returns More Than One Row

When you're updating using subquery, the subquery MUST return only one row. Otherwise you get this error message. Based on your query, it can be modified to a correlated query:

UPDATE TBLEWC_TASK_INSTANCE B
SET TASK_INSTANCE_ID =
(

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