An Introduction to Data Base Design by Betty Joan Salzberg (Auth.)

STATE Perhaps you are noticing that these are not useful bits of information about the real world, and in addition, the list might get quite long.

Keys 29 (2) If an attribute is never on the right-hand side of a dependency, then it must be in every key. This includes attributes listed in no dependency. (3) Take the set of attributes B determined by the attributes A in every key, but not contained in that set (A). These cannot be in any key, even if they are on the left-hand side of some dependency; they will always make a collection of attributes non-minimal. ) The problem is still impossible to do in one's lifetime in the general case. For example, if the closure of the list of dependencies is the list of dependencies we use, then everything is on the left and also on the right by rule 2 (augmentation).

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