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Getting DBMIN to ignore blank (null) dates?

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  • Getting DBMIN to ignore blank (null) dates?

    I am attempting to retrieve the earliest date in a "maintenance due" field of a child table in a set (One to many relation). This seems to work perfectly using dbmin() as long as there are no blank dates in the child records.

    However, if one of the child records has a blank in that field, then the function dbmin returns a blank as the earliest value. I do not want to include blanks in this result, but rather return the earliest date that is not blank (unless of course all child records are blank).

    Does anyone know a way to restrict dbmin to not return a value of blank if there is at least one non-blank entry?

    I know that tablemin() has the ability to filter the records returned, but it returns the minimum for the entire table, not just the records connected to the parent.

    Thanks for any help/ideas/workarounds you may be able to offer.

  • #2
    Re: Getting DBMIN to ignore blank (null) dates?

    Try a variation of your current dbmin expression and use


    as the final parameter (lookup expression as C).
    There can be only one.


    • #3
      Re: Getting DBMIN to ignore blank (null) dates?

      Thanks Stan,

      That is almost exactly what I need.

      Here is my calculated field:
      NextMainDue = dbmin("sequip1","Addressid",Id_S,"if(trim(cdate(Sequip1->Maintduedate))>'',Sequip1->Maintduedate,{12/31/2099})")

      This produces exactly what I need, except that if there are no dates at all in the child record, it shows as "12/31/2099".

      Any suggestions as to how to have it display a blank field instead of the "12/31/2099"? If I change the dbmin from {12/31/2099} to simply "", then the function seems to fail and returns nothing.


      • #4
        Re: Getting DBMIN to ignore blank (null) dates?

        Define an intermediary result

        im_rslt = dbmin("sequip1","Addressid",Id_S,"if(trim(cdate(Sequip1->Maintduedate))>'',Sequip1->Maintduedate,{12/31/2099})")


        NextMainDue = If(calc->im_rslt <> {12/31/2099},calc->im_rslt,{})

        Of course you could just collapse that to

        NextMainDue = If(dbmin("sequip1","Addressid",Id_S,"if(trim(cdate(Sequip1->Maintduedate))>'',Sequip1->Maintduedate,{12/31/2099})") <> {12/31/2099},dbmin("sequip1","Addressid",Id_S,"if(trim(cdate(Sequip1->Maintduedate))>'',Sequip1->Maintduedate,{12/31/2099})") ,{})
        Last edited by Stan Mathews; 02-15-2010, 03:17 PM.
        There can be only one.


        • #5
          Re: Getting DBMIN to ignore blank (null) dates?

          Thanks, Stan! Works exactly as I need now...

          I'm a little confused and would love to know why I couldn't simply substitute { } for {12/31/2099} in the first suggestion you made.

          I'm grateful to see it work right, but I'm one who always likes to know "Why?"

          Thanks again for the assistance!


          • #6
            Re: Getting DBMIN to ignore blank (null) dates?

            Originally posted by gkpurcey View Post
            I'm a little confused and would love to know why I couldn't simply substitute { } for {12/31/2099} in the first suggestion you made.
            Substituting {} in the first suggestion would have gotten you back to where you started. The parameter as suggested "says"

            compute the minimum of Maintduedate (if it is greater than {}) and {12/31/2099}

            so if the date is blank ({}) we pretend it is {12/31/2099} and trick the dbmin() function into never considering it as the minimum so long as there are valid dates.

            If I change the dbmin from {12/31/2099} to simply "", then the function seems to fail and returns nothing.
            You can't use "" because that is not a date value and dbmin() can't use it for comparison.
            Last edited by Stan Mathews; 02-15-2010, 03:37 PM.
            There can be only one.


            • #7
              Re: Getting DBMIN to ignore blank (null) dates?

              OK, that does make sense that the dbmin() function would require the last parameter to be of the same type as the column it's trying to evaluate.

              Thanks for the explanation.