Re: Nulls in oracle (ie, empty outer join records) cannot be compared

From: Andrus Adamchik (andru..bjectstyle.org)
Date: Sun Aug 20 2006 - 09:13:47 EDT

  • Next message: Andrus Adamchik: "Re: Idea for handling splits, possibly with only minor changes to alias table handling"

    Yeah, this is universal behavior, not specific to Oracle. In raw SQL
    I usually use "nvl", but I guess until we support functions in
    expressions, explicit null checking is required.

    Andrus

    On Aug 20, 2006, at 5:04 AM, Mike Kienenberger wrote:

    > Apparently, life gets worse. Oracle makes it very difficult to
    > compare outer join record values.
    > Nulls do not equal anything, nor do they "not equal" anything.
    >
    > http://thinkoracle.blogspot.com/2005/06/nulls-in-oracle.html
    >
    > So if I want to compare any column from a left outer join, I have to
    > explicitly handle the nulls somehow.
    >
    > For example, use nvl to provide an alterate default value whenever a
    > null is found.
    >
    > ( (nvl(RTRIM(t4.IS_ACTIVE), 'N') <> 'Y')
    >
    > Should something like this be automatically done for any outer join
    > implementation?
    >
    > We can't use nvl genericly, but we can add another clause:
    >
    > (x is null) or (x <> 'Y') for an inequality.
    > (x is not null) and (x = 'Y') for an equality
    >
    > Apparently the behavior can vary from database to database and even
    > between join and search clauses for some databases. No end of fun.
    >

    This archive was generated by hypermail 2.0.0 : Sun Aug 20 2006 - 09:15:12 EDT