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    <p>Your relation variable (relvar) indeed violates 1NF but perhaps not for the reason you are expecting: it is the presence of the null that violates 1NF. If you think your relvar contains a repeating group, think again.</p> <p>First normal form, or simply "normalized", is the minimum requirement for the relational model. To quote Chris Date:</p> <blockquote> <p>by definition, a null isn't a value. It follows that: A "type" that contains a null isn't a type (because types contain values); A "tuple" that contains a null isn't a tuple (because tuples contain values); A "relation" that contains a null isn't a relation (because relations contain tuples, and tuples don't contain nulls). In fact, nulls violate the most fundamental relational principle of all—viz., The Information Principle. The net of all this is that if nulls are present, then we're certainly not talking about the relational model (I don't know what we are talking about, but it's not the relational model); the entire edifice crumbles, and all bets are off.</p> </blockquote> <p>The point about repeating groups and 1NF is a tricky one to explain and I won't try. Instead, I urge you to read <a href="http://www.simple-talk.com/content/print.aspx?article=712" rel="nofollow">Facts and Fallacies about First Normal Form</a>, specifically the section "The ambiguity of Repeating Groups".</p> <p>Assuming the null was eliminated, the relvar would satisfy 1NF but note we would need further information (e.g. keys) to determine whether it would also satisfy higher normal forms.</p>
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    1. POIs this a 1NF failure?
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    1. COThis relation does contain a repeating group, the Phone Number group. Simply put, that is clearly observable from the relation above. The presence of the NULL value makes it a 1NF violation even more so. The main focus here is the creation of a group of elements where a limited number is desired.
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    2. CO@user: I see three distinct attributes named `Phone1`, `Phone2` and `Phone3` respectively; they could have been named `home_phone`, `mobile_phone` and `work_phone`, the names are not significant, ditto their types. I see no "Phone Number group".
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    3. COIn a logical data model, if the data types in the columns in an entity are similar, they are by definition a repeating group. The same would apply to Hobby1, Hobby2, Hobby3 or Sport1, Sport2, Sport3.
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