Constraints with several father tables

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  • Ralf
    #1

    Constraints with several father tables

    Hi,

    I have 4 tables: "T_father1",... ,"T_father4" .
    In relation to these father-tables I have a child-table: "T_Child"
    (with only 1 foreignkey-field: FsID) alread filled with some records.

    That means each record of "T_Child" has in its field "FsID" a primary
    key of one of the 4 father tables.

    If I want to create the 4 foreign-key CONSTRAINTS:
    "T_Child.Fs ID <-T_FatherX.ID" (X=1..4)
    I get an Oracle-error (Ora-02298): "cannot validate".

    My question is:
    How can I tell Oracle (how do I have to create the Constraint), that
    this foreignkey-field "T_Child.Fs ID" is not the foreign-key to ONE
    father-table but to FOUR father tables ?
    Or is this "bad database design" to have one foreignkey-field for 4
    father tables ?

    Thanks in advance for any help, suggestionst or comments !!
    Best regards
    Ralf Miko
    Tags: None
    • Sybrand Bakker
      #2
      Re: Constraints with several father tables

      Miko@boehrer.de (Ralf) wrote in message news:<fa624200. 0307240031.2027 8673@posting.go ogle.com>...
      Hi,
      >
      I have 4 tables: "T_father1",... ,"T_father4" .
      In relation to these father-tables I have a child-table: "T_Child"
      (with only 1 foreignkey-field: FsID) alread filled with some records.
      >
      That means each record of "T_Child" has in its field "FsID" a primary
      key of one of the 4 father tables.
      >
      If I want to create the 4 foreign-key CONSTRAINTS:
      "T_Child.Fs ID <-T_FatherX.ID" (X=1..4)
      I get an Oracle-error (Ora-02298): "cannot validate".
      >
      My question is:
      How can I tell Oracle (how do I have to create the Constraint), that
      this foreignkey-field "T_Child.Fs ID" is not the foreign-key to ONE
      father-table but to FOUR father tables ?
      Or is this "bad database design" to have one foreignkey-field for 4
      father tables ?
      >
      Thanks in advance for any help, suggestionst or comments !!
      Best regards
      Ralf Miko

      I wouldn't even call this design. Multiple foreign keys in multiple
      tables to 1 PK are definitely possible. One foreign key to multiple
      parents of course not.
      Your parent table must be falling apart in several subtypes. Hence you
      need to differentiate.

      Sybrand Bakker
      Senior Oracle DBA

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