SQL retain two decimal places

In SQL Server, Division occurs when the divisor is 0 and two decimal places are retained. The statement is as follows:
Select case when num = 0 then 0 else convert (decimal (210.343),/num) end as result from tabnumber

Select
[Carrier] As 'carrier group ',
Count (*) as 'zhangshu ',
'0' as 'ticketing efficiency ',
Sum (cast (sumprice as INT) as 'face price ',
Sum (cast ([taxprice] As INT) as 'infrastructure Bill ',
Sum (cast ([oilprice] As INT) as 'fuel Bill ',
Sum (cast (sumprice as INT)-cast ([flightback] As INT) as 'real billing'
From [order_flightdetail] group by [carrier] Order by count (*) DESC

Select
[Carrier] As 'carrier group ',
Count (*) as 'zhangshu ',
'0' as 'ticketing efficiency ',
Sum (convert (decimal (), sumprice) as 'face price ',
Sum (convert (decimal (), [taxprice]) as 'infrastructure Bill ',
Sum (convert (decimal (), [oilprice]) as 'fuel Bill ',
Sum (convert (decimal (), sumprice)-convert (decimal (), [flightback]) as 'real Bill'
From [order_flightdetail] Where [carrier] <> ''group by [carrier] Order by count (*) DESC