这应该可以解决问题...请查看 CASE WHEN

This should do the trick...please have a look on CASE WHEN

select i.Date, i.No,sum(CASE WHEN t.VAT<>'no'  THEN 
amount ELSE 0 END) as  Excluding_VAT,
sum(t.amt_vat)as vatamount,
sum(CASE WHEN t.VAT='no' THEN amount ELSE 0 END) as  NonVat,
sum(t.amt_vat+t.amount)as totamt
from a i join b t on i.ID=t.ID
where i.Date between '1991-11-18' and '1995-11-19'
group by i.ID,i.No,i.Date