sql update using select and sub select with joins - sql

Question

I have an update statement that I am using to change the value of my building field if certain criteria is met.
Here is where I tell it to set my building value to the result of my select statement
update Table set Building = (select case when child.date determined between child.entry date and child.withdrawal date
then child.building else child.[offender bldg]end
Then my select statement is then a product of another select statement where I have to define the value for date3 because it has nulls and I need it force it to be current date to ensure that I am capturing all the records that need to be updated.
from (select w.BUILDING, [Withdrawal Date] = case when WITHDRAWAL_DATE is null then GETDATE() else w.WITHDRAWAL_DATE end,a.DATE_DETERMINED,w.ENTRY_DATE,a.RESP_BUILDING,o.BUILDING[Offender Bldg]
from dbo._temp_disc_off a inner join dbo.offender o on (a.INCIDENT_ID = o.INCIDENT_ID) inner join dbo.entry w on (o.PERSON_ID = w.STUDENT_ID))child</b>
This next section is associated to the first select statement and filters for buildings that meet either criteria
where child.DATE_DETERMINED between child.ENTRY_DATE and child.[Withdrawal Date] and child.RESP_BUILDING is null
or child.DATE_DETERMINED between child.ENTRY_DATE and child.[Withdrawal Date] and child.RESP_BUILDING <> child.[Offender Bldg])</b>
I have to set it up this way, because I need to compare to a date and not a null value because my result set goes from 2425 to 461 if I don't set withdrawal date to getdate() if null.
When I run the query I get the following error:
Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.
I know that it is trying to return multiple values, and that is what I want. But when I try to use IN instead of = I get an incorrect syntax error.
The statement is not being used in a stored procedure, I am just trying to mass update some records. Please help, and please over look the fact that my syntax is a little off.
Thanks in advance
Updated My Question with Full Block
*here is my full statement in one block, I made some changes to it since posting, but I am trying to do the same update the temp disc off action table resp_building field. I can only do this if the date_determined is between the entry and withdrawal dates, but in some cases the withdrawal date is null, so I add a sub select where I provide a value for withdrawal date.
update dbo._temp_disc_off_action
set RESP_BUILDING = (
select case when child.DATE_DETERMINED between child.entry_date and child.[Withdrawal Date]
then child.BUILDING else child.[Offender Bldg] end
from (
select w.BUILDING, [Withdrawal Date] = case when WITHDRAWAL_DATE is null
then GETDATE()
else w.WITHDRAWAL_DATE end,
a.DATE_DETERMINED, w.ENTRY_DATE, a.RESP_BUILDING, o.BUILDING [Offender Bldg]
from dbo._temp_disc_off_action a
inner join dbo.DISC_OFFENDER o
on a.INCIDENT_ID = o.INCIDENT_ID
inner join dbo.REG_ENTRY_WITH w
on o.PERSON_ID = w.STUDENT_ID
where w.BUILDING = 41) child
where child.DATE_DETERMINED between child.ENTRY_DATE and child.[Withdrawal Date]
and child.RESP_BUILDING is null
or child.DATE_DETERMINED between child.ENTRY_DATE and child.[Withdrawal Date]
and child.RESP_BUILDING <> child.[Offender Bldg])

Answer 1

The problem is:
update Table set Building = (sub query).
What you are trying to do is update a single column, Building, with a single value returned from the sub query. However, your sub query is returning more than one value. So instead of Building 4, it gives you Building 4, 10, and 19. Sql Server can't set a single column to multiple values and throws the error.
The easiest way to debug is to convert your entire update statement into a select statement that selects the original value and the value you want to update to. You can examine the result select and see why you have duplicate rows from your sub select and figure out how to return a single value, or potentially concatenate or group multiple rows together to return a single value.

Answer 2

I figured it out, I was completely over complicating things and was able to update the fields I wanted by simply running a statement where I included CASE statement in my where clause. That allowed me check if the date determined is between the two dates, while replacing null values of my withdrawal date with current date. Here is my statement below:
UPDATE dbo._temp_disc_off_action SET RESP_BUILDING = w.BUILDING
FROM dbo._temp_disc_off_action a JOIN dbo.DISC_OFFENDER o ON (a.INCIDENT_ID = o.INCIDENT_ID) JOIN dbo.REG_ENTRY_WITH w ON (o.PERSON_ID = w.STUDENT_ID)
WHERE a.DATE_DETERMINED BETWEEN w.ENTRY_DATE AND CASE WHEN w.WITHDRAWAL_DATE IS NULL THEN GETDATE() ELSE w.WITHDRAWAL_DATE END AND a.RESP_BUILDING IS NULL AND **o.BUILDING = '41'
**OR a.DATE_DETERMINED BETWEEN w.ENTRY_DATE AND CASE WHEN ** w.WITHDRAWAL_DATE **IS NULL THEN GETDATE() ELSE w.WITHDRAWAL_DATE END
AND a.RESP_BUILDING <> o.BUILDING AND o.BUILDING = '41'