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Difference between 0 and null in numeric field in a grid

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    Difference between 0 and null in numeric field in a grid

    Trying to define a conditional image based on a numeric field (column) that contains either 0, 1 , 2 or 3 or null. The problem is, it doesn't seem to know the difference between null and 0 - both evaluate to true.

    Is there a way to tell if a numeric field is null in a conditional expression?
    - Dan Hooley
    - Custom Desktop or Web database development -

    #2
    Re: Difference between 0 and null in numeric field in a grid

    Hi Dan

    x = "" would be different to x = 0 for server side expressions

    x= '' for client side
    Glen Schild



    My Blog

    Comment


      #3
      Re: Difference between 0 and null in numeric field in a grid

      Hi Glen,

      My expressions are client side. From what I'm seeing, both of these evaluate to true, whether the field contains a null value or 0:

      x = ''
      x = 0
      - Dan Hooley
      - Custom Desktop or Web database development -

      Comment


        #4
        Re: Difference between 0 and null in numeric field in a grid

        hello
        this was discussed before,
        as far as alpha is concerned there is no difference between null an zero.
        it will evaluate the same.

        ps: http://wiki.alphasoftware.com/Null+Table+Field+Values
        Last edited by GGandhi; 02-18-2013, 07:27 PM. Reason: added wiki link
        thanks for reading

        gandhi

        version 11 3381 - 4096
        mysql backend
        http://www.alphawebprogramming.blogspot.com
        [email protected]
        Skype:[email protected]
        1 914 924 5171

        Comment


          #5
          Re: Difference between 0 and null in numeric field in a grid

          The wiki link is in relation to dbf, my database is sql, if that makes any difference.

          I got around it by creating an expression for the field in the SQL builder (the grid is based on a SQL Select Statement) that converts null values to -1:
          if(fieldname IS NULL , -1, fieldname) as fieldname

          And then just test for -1 instead of null. Seems to work ok. Open to other ideas, if anyone has any.
          - Dan Hooley
          - Custom Desktop or Web database development -

          Comment


            #6
            Re: Difference between 0 and null in numeric field in a grid

            Dan, I think your way (or variants of it) is typically the best way to do it. You have to differentiate a NULL from a value at the source before it enters the Alpha world.

            Comment


              #7
              Re: Difference between 0 and null in numeric field in a grid

              hello

              i concur with andy, your way of fixing the null value before alpha evaluates it would be the best way, the alpha has dbf format of thinking even when the source is from sql. it is alpha that is evaluating.
              so feeding a non null value and a value to compare would the best answer.
              thanks for reading

              gandhi

              version 11 3381 - 4096
              mysql backend
              http://www.alphawebprogramming.blogspot.com
              [email protected]
              Skype:[email protected]
              1 914 924 5171

              Comment


                #8
                Re: Difference between 0 and null in numeric field in a grid

                Originally posted by danh View Post
                The wiki link is in relation to dbf, my database is sql, if that makes any difference.

                I got around it by creating an expression for the field in the SQL builder (the grid is based on a SQL Select Statement) that converts null values to -1:
                if(fieldname IS NULL , -1, fieldname) as fieldname

                And then just test for -1 instead of null. Seems to work ok. Open to other ideas, if anyone has any.
                Hi Dan,
                You can use "COALESCE(fieldname, -1) AS fieldname" in your SQL statement not in the SQL builder, or better yet, create a view and just use the view as your source.
                Edhy Rijo
                Progytech
                (Computer Consultants)
                The makers of CardTracking.Net
                www.progytech.com

                Comment


                  #9
                  Re: Difference between 0 and null in numeric field in a grid

                  I would agree, dealing with this in a view or stored procedure before it even hits alpha is the way to go, let the server take the strain rather than alpha.
                  Glen Schild



                  My Blog

                  Comment

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