Division by 0

How do I add an if statement to check for sum(n.shippedQtyLy)=0
(sum(n.scanQtyLy)*100)/sum(n.shippedQtyLy) as scanPerQtyLy,

When I try
 if sum(n.shippedQtyLy)=0 then 0 else
(sum(n.scanQtyLy)*100)/sum(n.shippedQtyLy) as scanPerQtyLy,
I get a syntax error


select n.category,d.item_desc,n.bill_id,n.sku_no,n.pricegroup,avg(n.retail_pr) as retail_pr,

sum(n.shippedQtyLy) as shippedQtyLy,sum(n.shippedAmoutLy) as shippedAmoutLy,avg(n.shippedItemPriceLy) as shippedItemPriceLy, --shipped last year      
sum(n.scanQtyLy) as scanQtyLy,sum(n.scanAmoutLy) as scanAmoutLy,avg(n.scItemPriceLy) as scItemPriceLy,                                 --scan last year
(sum(n.scanQtyLy)*100)/sum(n.shippedQtyLy) as scanPerQtyLy,(sum(n.scanAmoutLy)*100)/sum(n.shippedAmoutLy) as scanPerAmountLy,  --scan % last year