sql语句的有关问题，主要是后面的条件

sql语句的问题，主要是后面的条件
select Supplyid,SupplyState, SupplyPrice,SupplierMark from PurchasePrice where 
Operators='LT' and Province='SD'and Par='100' and SupplyState!=-1 and Code ='0531'or code='' order by SupplyPrice asc




帮忙看一下sql语句那地方错了！！我要实现符合前面条件的数据 ，code字段为某个值或位空！！

怎么写到底！！
请教各位大侠！！！

------解决方案--------------------------------------------------------
select Supplyid,SupplyState, SupplyPrice,SupplierMark from PurchasePrice where 
Operators='LT' and Province='SD'and Par='100' and SupplyState!=-1 and （ Code ='0531'or code='' ）order by SupplyPrice asc 
需要加个括号就对了