Question

I have this query

select devlocview.ENTERPRISENAME
FROM AlarmDeviceView alrmDevView
INNER JOIN devicelocationview devLocView 
    ON devlocview.oid=alrmdevview.deviceoid
LEFT OUTER JOIN DEVICEGROUPVIEW devGrpView 
    ON devlocview.oid=devgrpview.deviceoid
LEFT OUTER JOIN RackCapacityView rackCapView 
    ON devlocview.RACKID=rackCapView.oid
WHERE 
(
    alrmdevview.createddate = ( select max(alview.createddate) 
                                from alarmdeviceview alview 
                                WHERE alview.alarmoid=alrmdevview.alarmoid) 
    or alrmdevview.createddate IS NULL
)
AND devlocview.ENTERPRISENAME='Enterprise1'
AND devlocview.buildingname in (
CASE
WHEN $p{building} IS  not NULL THEN $p{building}
WHEN $p{building} IS  NULL THEN (select buildingname from cdmr.devicelocationview)
END
)

Here this part "select buildingname from cdmr.devicelocationview" returns multiple rows due to which I am getting

exception as 01427. 00000 – “single-row subquery returns more than
one row”

As per the requirement I want to assign multiple building when $p{building} is null

Answer 1

A CASE is a scalar expression, it must evaluate to a scalar value. You can’t use it to return a multi-row set.

The most common idiom I’ve seen for varying the condition based on whether an input value is NULL would look like this for your example:

AND (  ( $p{building} IS NOT NULL AND devlocview.buildingname = $p{building} )
       OR
       ( $p{building IS NULL AND devlocview.buildingname IN (SELECT buildingname FROM  cdmr.devicelocationview ) )
    )