Re: Primary Key and Unique Key

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From: argusy (argusy_at_slmember.on.net)
Date: 08/23/04

  • Next message: Lishi Liu [MSFT]: "RE: Primary Key and Unique Key" 
    Date: Mon, 23 Aug 2004 21:43:02 +0930

    yes.
    You might get garbage, but you can relate any key to any field in any other table.
    i.e.
    T1

    ID (autonumber) primary, unique
    ClassID (number) not unique
    StudentID (number) unique
    surname (text) no key
    Firstname (text) no key

    T2

    ID (number) primary, unique
    subject (text) not unique

    I could relate T1 studentID with T2 classID, but that would be stupid
    I could relate T1 ID with T2 studentID, (again stupid)
    I could relate T1 classID with T2 ID, and this WOULD be useful

    none (except one is declared as "primary")

    The primary key is the one you've declared as primary.
    (It may or may not be unique, but always take the view that any primary key you declare IS
    unique)

    Argusy

    fniles wrote:
    > Thanks. I am still confused.
    > So, does it mean that both primary key and unique keys
    > can also be related to other tables ?
    > So, what are the difference between the two keys ?
    > What are the difference between primary key and the
    > secondary keys ?
    > Thanks.
    >
    >
    >>-----Original Message-----
    >>"Fie Fie Niles" <fniles@wincitesystems.com> wrote in
    >
    > message
    >
    >>news:%23tvz2UwhEHA.704@TK2MSFTNGP12.phx.gbl
    >>
    >>>Is it correct that primary key can be related to other
    >>
    > tables, but
    >
    >>>unique keys don't ?
    >>
    >>No
    >>
    >>--
    >>Reply to the group so all can participate
    >>VB.Net... just say "No"
    >>
    >>.
    >>
    >

  • Next message: Lishi Liu [MSFT]: "RE: Primary Key and Unique Key"

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