= Multivalued dependency
{title2=$X\twoheadrightarrow Y$}
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= MVD
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{synonym}
For <database tuples> agreeing on $X$, requires the combinations obtained by swapping their values on $Y\setminus X$ and on the remaining <database attributes> to occur too. A <functional dependency> implies the corresponding <multivalued dependency>; complementation exchanges $Y$ with the remaining <database attributes>. A <multivalued dependency> is trivial if $Y\subseteq X$ or $X\cup Y$ is the full <relational schema>.
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