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Explain Multivalued Dependency?

Answer»

Multivalued dependency denoted by X-->Y specified on RELATION schema R, where X and Y are both subsets of R, specifies the FOLLOWING CONSTRAINT on any relation r of R: if two tuples t1 and t2 EXIST in r such that t1[X] = t2[X] then t3 and t4 should also exist in r with the following properties

  • t3[x] = t4[X] = t1[X] = t2[X]
  • t3[Y] = t1[Y] and t4[Y] = t2[Y]
  • t3[Z] = t2[Z] and t4[Z] = t1[Z]

where [Z = (R-(X U Y)) ]

Multivalued dependency denoted by X-->Y specified on relation schema R, where X and Y are both subsets of R, specifies the following constraint on any relation r of R: if two tuples t1 and t2 exist in r such that t1[X] = t2[X] then t3 and t4 should also exist in r with the following properties

where [Z = (R-(X U Y)) ]


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