update docline set  
 SUNIT = (select wunitid from stock where WStockid = docline.wstockid) ,
 FUNITQTY = coalesce((select unit.Funitqty from stock join unit on unit.Wunitid = stock.wunitid where WStockid = docline.wstockid),1) 
 where 
 WDOCID = <@KEY@>