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The Relational Database Dictionary, Extended Edition by C. J. Date

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Chapter 22. U

UDO User defined operator.

UDT User defined type.

unary Of degree one.

UNGROUP See ungrouping.

ungrouping Let s be a relation with an attribute YR of type RELATION {Y}, and let {X} be the set of all attributes of s except YR. Let {Y} have attributes Y1, Y2, . . ., Yn; also, let {X} not contain any attribute with the same name as any of Y1, Y2, . . ., Yn. Then the ungrouping s UNGROUP (YR) is another relation r. The heading of r consists of the set theory union of {X} and {Y}. As for the body, let z be a relation with heading consisting of {X} extended with an attribute YT, of type TUPLE {Y}, and body defined as follows: for each tuple of s, z contains a set of tuples, one (t, say) for each tuple in the YR value in that s tuple; each ...

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