Question

I need to select and update a table looking up values from other tables. The idea is to select some details from order, but get the names of the foreign key values using the id

For the select I tried:

SELECT [Order].order_date, 
       [Order].total_price, 
       [Order].order_details,
       vehicle.reg_no,
       Staff.name,
       stock.name 
FROM 
       Order,
       vehicle,
       staff,
       stock
WHERE
      order.id = @order_id 
  AND vehicle.id = Order.vehicle_id 
  AND staff.id = Order.staff_id 
  AND stock.id = Order.product_id

for the update that i tried

UPDATE order 
SET 
    total_price = @total_price, 
    order_detail = @order_detail,
    product_id = (select is from stock where name = @product_name), 
    customer_id = (select id  from customer where name = @customer_name), 
    vehicle_regno = (select reg_no  from vehicle where name = @name)
WHERE (id = @id)

both does not return anything. i hope am clear enough to get some help, but if not pls i will provide more info.

thanks for helping

Answer 1

You might want to try converting you INNER JOINs to a LEFT JOIN for the SELECT statement.

SELECT [Order].order_date, 
       [Order].total_price, 
       [Order].order_details,
       vehicle.reg_no,
       Staff.name,
       stock.name 
FROM 
       [Order] 
       LEFT JOIN vehicle
       ON vehicle.id = [Order].vehicle_id 
       LEFT JOIN staff
       ON staff.id = [Order].staff_id
       LEFT JOIN stock
       ON stock.id = [Order].product_id
WHERE
      [order].id = @order_id 

The reasons why this would make a difference is if either a) you allow nulls in the fk fields or b) you don’t have fk contraints which may point to a problem with your design.

Your update statement should update some rows provided that the value of @id exists in the ORDER table but as @Danny Varod already commented you won’t get rows back only the number of rows affected