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Thread: cascading dropdown box when the preceding value is NULL

  1. #1
    Member
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    Malcolm Harison
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    May 2012
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    Whakatane, New Zealand
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    168

    Default cascading dropdown box when the preceding value is NULL

    Greetings,

    I need to help the user to select the right value by narrowing their choice using a series of cascading dropdown boxes, until they reach a unique record to select.

    The three fields are Level 1, Level 2 and Level 3 - nice and simple so far. The cascade option in the dropdown box works like a treat - until it comes across a null value in Level 2. A very few rows (of the hundreds) only have a value in Level 1 - because the level 1 defines them as unique.

    In the above case, the dropdown box for Level 3 has only a NULL to base its selection on, so there is no value - and the UX doesn't accept that. So the user can't make a selection.

    Can I somehow 'disable' the lower level dropdowns, and get the final one to point to the last 'not-null' value? How have others handled this issue?

    Many thanks

    Malcolm

  2. #2
    "Certified" Alphaholic
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    Larry Grupido
    Join Date
    May 2010
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    1,820

    Default Re: cascading dropdown box when the preceding value is NULL

    The easiest solution is to make sure the scenario you are experiencing doesn't happen. Fix the data so there is ALWAYS a Level 2 for every Level 1, even if the Level 2 value is just a placeholder value.

    If you can't do that, then you are going to have to buffer it with some scripting and you likely won't be able to use the built in cascading drop down method.

  3. #3
    Member
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    Sean OKelly
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    Sep 2015
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    Charleston, WV
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    Default Re: cascading dropdown box when the preceding value is NULL

    You would need to add custom script to return the number of sub records. You can call the same function each time, passing in the table and field to query. If the return record set has no records, then disable the other controls. There is action javascript to return records based on a form field.

  4. #4
    Member
    Real Name
    Malcolm Harison
    Join Date
    May 2012
    Location
    Whakatane, New Zealand
    Posts
    168

    Default Re: cascading dropdown box when the preceding value is NULL

    Thanks both, in this case the 'easy out' is probably the most practical solution - I just hadn't thought of it! Thx again

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