roots

select a, b, c, x1, iif(x2=x1, NULL, x2) x2
from
(
    select *, iif(d>0, (-b+sqrt(d))/2/a, iif(d=0,-b/2/a,NULL)) x1, iif(d>0, (-b-sqrt(d))/2/a, iif(d=0,-b/2/a,NULL)) x2
    from
    (
        select *, b*b-4*a*c d
        from
        (
            select distinct B_Q_ID a, B_V_ID b, B_VOL c
            from CTE
        )t
    )t
)t