条件表更新SQL Server 2008

Question

I want to update table column where value taken from different column of same table, with condition that CompletionDate='1900-01-01 00:00:00.000'

How can I do it?

update Details 
set CompletionDate = (select FixedDate from TblRequirementDetails)
where CompletionDate = '1900-01-01 00:00:00.000'
and StatusID = '10'
GO

produces an error

Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.

Answer 1

It is very unclear on how you want to select the fixed date to set so. By your comments it is clear that you want to set the CompletionDate to FixedDate of same table when StausID=10 for fixedDate and I am assuming that It will give you the uniq row.

        UPDATE Details
        SET CompletionDate = FixedDate
        WHERE
             CompletionDate='1900-01-01 00:00:00.000'
             AND StausID= '10'

I am including to make sure that The subquery returns only one row. Bu this is very error prone approch and you need make sure that the Top 1 row is what you want to use.

---

UPDATE
As fromm comment I understood as you just want to update the same rows Complettiondate with that rows FixedDate value so updated the query.

Answer 2

Your sub query returns many result. Your sub query should only give a 1 value result. See query below

UPDATE Details 
SET CompletionDate = (
SELECT 
      FixedDate 
FROM TblRequirementDetails <WHERE CLAUSE HERE THAT ENABLES YOUR QUERY TO RETURN ONLY ONE VALUE>
)
WHERE CompletionDate='1900-01-01 00:00:00.000'
AND StatusID='10