select 
    g.Custid, 
    g.Grno, 
    g.Name, 
    case when c.Chno = 123 then c.Chno else null end Chno, 
    case when c.Chno = 123 then c.Chdate else null end Chdate 
from 
    GrfileB g 
    join Challan c on g.Grno = c.Grno
where 
    g.Custid = 1 
order by 
    g.Grno