update missing/bad date values with values from previous record

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  • Takeadoe

    #1

    update missing/bad date values with values from previous record

    First, let me say that I'm brand new to Access, so please assume I know
    nothing. I've got a table (210k records) of deer harvest information.
    Date of harvest is one of many variables in the table. Since our
    season runs from the first SAT in October to 31 January, valid harvest
    dates for 2005-06 were 4 Oct 2005 to 31 Jan 2006. Many records will
    have missing or dates outside of this range. Date is needed to assign
    each dead deer to a season (Gun, Archery, Muzzleloader, etc). For some
    seasons, like Gun, season can be had from WEAPON TYPE, which is one of
    the variables on the form. This is possible because there is only one
    season where a shotgun is allowed. Problem is, the bow can be used in
    3 seasons, so weapon type doesn't tell you what season it should be in.
    Long story short, I ultimately want to assign each record a valid date
    value. In the past, I've used SAS for this purpose. I do this in two
    steps. First I create a variable that identifies whether or not the
    date if valid. Then I use a retain statement which holds the value of
    date from the previous record and assigns it to the current record when
    the date flag is "invalid." In other words, the date from the most
    recent valid date is retain and dumped into those records with invalid
    dates. This continues until the flag switches to valid, at which time
    the retain value is updated. I wont bore you with the details as to
    why this is a reasonable approach, but if you're interested, let me
    know.

    So, you guessed it, can someone tell me how to use an update query to
    accomplish this?

    I would really appreciate any help you might be able to offer.

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