Re: The BOOLEAN data type

71062.1056_at_compuserve.com (--CELKO--) wrote in message news:<c0d87ec0.0304021755.5975f3da_at_posting.google.com>...
> >> I *think* that the idea was apps that use (or would like to) a
> boolean value
> for (say) SHIPPED on an order item line. <<
>
> And we need to know the actual ship date, so let's put in a column for
> that. Now the SHIPPED bit is redudant.

In that case the SHIPPED attribute should be a derived attribute. But you can not do that with SQL.

In a recent database design I used a PRINTED boolean attribute, and the customer is not interested on the actual print date.

I have another boolean attribute called InDeposit.

> Actually dangerous; someone
> sets the flag but doe snto give a date, or gives a date, but does not
> set the flag.

Derived attributes and integrity constraints are for that.

Regards
  Alfredo Received on Thu Apr 03 2003 - 16:23:53 CEST