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Thread: Constrain insert on duplicate in other table

  1. #1
    Registered User

    Constrain insert on duplicate in other table

    I'm trying to figure out if there's a way to do a unique check across multiple tables. I'm checking the users ip for a survey, and we're creating a new one in which we don't want people who took the first one to take. I'm wondering if it's possible to do this in 1 statement? I know I can easily do this in 2 statements with a bit of server side logic, but I'm more curious about it in an educational way.

    If MySQL were to support constraints would I be able to do a CHECK (count(table.ip) = 0), or would that not be possible since I'm referencing a different table? What would be the proper way to do that?

    Thanks to anyone who knows!

  2. #2
    hugeExplosions = true;
    The question is - why would you want to do this? Your IP information should only be contained in one table - you should not have multiple tables which contain a users IP address or you are creating data redundancy

    Can you describe your setup in more detail?
    MS Paint FTW!

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