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the update() function in a trigger

  • July 4, 2003 at 11:20 am

    #82708

    I just need a quick clarification to see if I understand this function. When I have a trigger that fires on an INSERT or UPDATE, if I use the update() function within the trigger, the code within the update() test will not run if there is no value for the column I'm testing. What I'm also wondering is how NULLs factor into that. Will the INSERT of a NULL cause the update() to be true?

    Thanks!

  • July 4, 2003 at 10:42 pm

    #464212

    The INSERT of NULL will cause UPDATE() to be true for that column, regardless of whether the NULL is explicitly supplied or implicit (by omitting it from the values list)


    Cheers,
    - Mark

  • July 5, 2003 at 12:29 pm

    #464216

    So when will an update() be false?

  • July 5, 2003 at 3:23 pm

    #464218

    When you UPDATE the row but not SET that particular column to any value


    Cheers,
    - Mark

  • July 7, 2003 at 9:16 am

    #464337

    That means that if I have a table Testing with col1, col2, col3, col4, and I did an insert like so:

    INSERT INTO Testing(col1, col2, col3, col4)

    VALUES('a', 'b','','d')

    and the update() tests col3 then it will be false?

  • July 7, 2003 at 2:38 pm

    #464387

    No, I was saying that the INSERT INTO command will return true for update() for all columns, regardless of whether NULLS or empty strings are assigned.

    The following will return false for update() of col3:

    UPDATE Testing SET col1='a', col2='b', col4='d' WHERE .....


    Cheers,
    - Mark

  • July 7, 2003 at 3:45 pm

    #464393

    Okay, thanks. That helps me understand it better. But , if you are using it in a trigger that fires AFTER an INSERT or UPDATE, it's useless for the insert right?

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