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  1. #1
    Zarah is offline Senior Member
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    Default Why doesn't an RDBMS allow repeating groups/arrays as column values?

    Integrity Rules

    Relational tables follow certain integrity rules to ensure that the data they contain stay accurate and are always accessible. First, ...

    A second integrity rule of the traditional relational model is that column values must not be repeating groups or arrays.
    Source.

    The question is that why wouldn't an RDBMS allow an Array (or any Collection) as the value of a column for a row?

    Like, duplicate rows are not allowed, and there is a reason/explanation for that, i.e. say there was a bank database and duplicate rows were allowed, and customers A and B represented two duplicate rows; and there came a situation when we needed to access/make a change to the bank balance of A, how would we know which row represents A.

    Likewise, what is the explanation for not allowing Arrays as values of a column?

  2. #2
    benji2505 is offline Senior Member
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    Default Re: Why doesn't an RDBMS allow repeating groups/arrays as column values?

    This is the 1st normal form of relational databases. It requires "atomic" data- keeping, which tries to avoid duplicates. It also excludes records with variable length, which has to do with the datamanagement of the program itself. Search for "4 normal database" and you will find plenty of info.

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