sum(InItem.qty_Invoiced  * InItem.cost) as "Total Cost"

select inv.Cust_num,

COUNT(inv.Cust_num)AS "Total Orders" 
--sum(InItem.qty_Invoiced  * InItem.cost) as "Total Cost"


from inv_hdr inv
inner join custaddr cust on inv.cust_num = cust.cust_num 
--left join inv_item InItem on  InItem.inv_num  =  inv.inv_num 
where cust.cust_seq = '0' and inv.cust_Num ='FER001S'
group  by inv.Cust_num, cust.name

Select cust.Cust_num,cust.name,
COUNT(distinct inv.Cust_num)AS "Total Orders" 
Sum(inv.qty_Invoiced * inv.cost) as "Total Cost"
from custaddr cust
inner join
(
Select distinct cust_Num,isnull(qty_Invoiced,0)qty_Invoiced,isnull(cost,0)cost
from inv_hdr inv
left join inv_item InItem on  InItem.inv_num  =  inv.inv_num 
)inv on inv.cust_Name = cust.cust_Name
Where cust.cust_seq = '0' and inv.cust_Num ='FER001S'
Group by cust.Cust_num,cust.name