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NULL

  • September 4, 2012 at 5:05 pm

    #1533579

    SQL Kiwi

    It drives me nuts to see column definitions without a NULL or NOT NULL constraint.

    +1

    g_one_2020

    As per the post, NULL may be NOT EQUAL to 2, so we should get rows with NULL values as well...

    But, I'm not getting the rows with NULL values. Just getting rows with c2=3 and 4.

    Ah, but NULL may be EQUAL to 2, as well. 😀

    It helped my understanding of NULLs to think of them as, basically, :unsure:, or "I've no clue"

    So, what does :unsure: = 2 evaluate to?

    I've no clue. So when you ask to find those rows where EmpPlace is NOT a specific value, SQL goes "Yes, No, No clue" and only returns those row where the answer is a definite Yes (that is, Yes, it's not that value)

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