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  1. Inherited Constraints

    by , 2-Oct-2009 at 09:00 AM (Development Team Blog)
    Today we set out to answer the age old question of:

    Should a child be judged by the sins of their parent?

    In my previous article Using Expressions and Properties in Constraints we talked about how constraints are inherited. In addition to any constraints that may be applied directly in a main Data Dictionary Object (DDO) that main DDO will also acquire the constraints from its parent DDOs. If this is not clear, you might want to review that article before proceeding. ...
  2. Constraints and Performance

    by , 19-Aug-2009 at 08:00 AM (Development Team Blog)
    Constraints again, who knew there could be so much to say about that. In some [URL="http://support.dataaccess.com/Forums/blog.php?b=17#comments"]comments[/URL] to an earlier post about constraints, the question about ordering of constraints and the impact on performance came up. John Tuohy then also mentioned in his [URL="http://support.dataaccess.com/forums/blog.php?b=25"]follow-up article about constraints and properties[/URL] that "The constraints are split up into multiple ...
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  3. Using Expressions and Properties in Constraints

    by , 14-Aug-2009 at 08:00 AM (Development Team Blog)
    In Sonny Falkís blog about constraints and local variables he noted that you should never use local variables inside of a Constrain As expression. In talking about Constrain As he states:
    You constrain against an expression, and the expression can be anything at all, including function calls executing DataFlex code and everything.
    Letís explore the use of Constrain As to call DataFlex functions and uncover one of the little secrets of inherited constraints.

    Constraints and User ...

    Updated 14-Aug-2009 at 08:36 AM by Stephen W. Meeley (Minor formatting.)

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  4. Constraints and Local Variables

    by , 10-Aug-2009 at 07:00 AM (Development Team Blog)
    Constraints and local variables is a frequent question in the forums, let's see if we can sort this out. The basics is that you set it up once, and then the runtime uses the constraints when finding records thereafter. If you want to change your constraints, you rebuild the whole set of constraints, and then the runtime uses that thereafter.

    The way constraints are set up is complicated a little with DDs and I won't go into the details, but essentially you augment the [I]OnConstrain[/I] ...