Question

I have a table of orders with orderID. I want when I create a new row in orders, and automatically have it add the same orderID to a new row in orderDetails. I got the auto incrementing to work, however whenever I try to link the two, adding cascade delete, it gives me an error.

‘order’ table saved successfully
‘orderDetail’ table
– Unable to create relationship ‘FK_orderDetail_order’.
Cascading foreign key ‘FK_orderDetail_order’ cannot be created where the referencing column ‘orderDetail.orderID’ is an identity column.
Could not create constraint. See previous errors.

Which seems to be because of the fact there is no orderID at row creation. Without these two linked it’s pretty hard to link an order to its information.

I am using Microsoft SQL server mgt studio. I learned via command-line MySQL, not SQL, so this whole GUI stuff is throwing me off (and I’m a tad rusty).

Answer 1

Your problem is that ‘orderDetail.orderID’ should not be an identity column (auto-incrementing). It should be based on the orderId in the Order table. You can do that in a variety of ways. If you are using stored procedures, and making separate calls to the database for the orderDetail records, have the code save the order row first, and return the newly created OrderId value, then use that value on the calls to save orderdetails. If you are making one call to a stored proc that saves the order header record and all order detail records in one call, then in the stored procd, insert the ordfer record forst, use Scope_identity() to extract the newly created orderId into a T-SQL variable,

  Declare @orderId Integer 
  Insert Orders([Order table columns]) 
  Values([Order table column values])
  Set @orderId = scope_Identity()

and then use the value in @orderId for all inserts into the OrderDetails table…

  Insert OrderDetails(OrderId,  [Other OrderDetail table columns]) 
  Values(@orderId , [Other OrderDetail table column values])