>>>>Gregory,
>>>>
>>>>In my case the child table does have these fields (I don't know you remember an example I described in another thread). For example, the parent table (Accounts) will have fields COST_CENT (char) and SITE_NO (int)). And the child table (Purchase orders) will have the same two fields COST_CENT (char) and SITE_NO (int). If user will change the value in the COST_CENT of the parent table, all POs where this value is set should be changed. Hence the need for the constraint with cascading update.
>>>>
>>>>
>>>
>>>if Accounts has (amongst other fields)
>>>
>>>Accounts_pk
>>>Accounts_cost_cent
>>>Accounts_Site_no
>>>
>>>Then, the PO table should only have an Accounts_fk, since Site_no and cost_cent can be retrieved with an sql join
>>>
>>>If you do not store the cost center and the site_no in the PO, then you do not need a cascading update - do you ?
>>
>>I see what you are saying. But this would be the case if I designed the application right in the first place <g>.
>
>haha - there are exceptions though
>
>I have a customer who has a tariff for certain types of work
>
>eg, for this type of work
>- charge a minimum of $150.00 including half an hour of work
>- above half an hour of work, $100.00 an hour extra
>
>The employees enter a customer number, a date, time from- to and a work code
>
>At a certain point in time an invoice is made
>
>I then copy the details of the tariff (minimum, including, rate above including) to the invoice line
>
>The invoice line contains all the details of how we got to the amount billable of that line
>
>The reason I copy ( and do not store a fk in the invoice line) is that the tariff changes say each year (as life gets more expensive)
>
>If I look at the detail of an invoice of a couple of years back, I will see the tariffs that were applicable at that time (date of invoice)
>Had I stored the fk, the calculation would not make sense

Makes sense what you are doing. I have a similar part in my application where the employee rates are stored in the "charge" table; since the rate in the Employee Table will change and it is important to know what the charges were at the time when charges were made.