I have this query

insert into A 
select 1,99,'ABC'
union
select 2,99,'5-0-0'
go

insert into B
select 1, 'ONE'
union
select 2, 'TWO'

;with dt as (
    select cast(replace(CODEVALUE,'-','') as int) VAL 
    from A
    join B on B.CODEID=A.CODEID and B.CODENAME='TWO' and A.PRJID=99
)

select MSG from (
    select case when VAL>25 then 'BRAVO' end MSG from dt
) q
where MSG is not null

I expected to return MSG, not error

But if I remove

where MSG is not null

it works