sql server - SQL Northwind Practice -

i have practice question:

show each order item – customer name , order id, product name, ordered quantity, product price , total price (ordered quantity * product price) , gap between ordered date , shipped date (the gap in days). order order id.

northwind of course.

my query was:

select      c.contactname, o.orderid, p.productname,      od.quantity, od.unitprice,      od.quantity * od.unitprice [total price]      orders o, customers c, products p, [order details] od      c.customerid = o.customerid     , o.orderid = od.orderid     , od.productid = p.productid order      o.orderid; 

the thing not is: "gap between date , shipped date". don't it.

thanks.

pertinent question, gap between ordered date , shipped date refers calculated value of:

datediff(day, date_ordered, date_shipped) gapdays 

using sql datediff() function, date_ordered , date_shipped corresponds field names in table (you may need rename them per actual fields; also, correct join syntax explained here; https://msdn.microsoft.com/en-us/library/zt8wzxy4.aspx).

hope may help.