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Do we need to create a separate table for each of the multivalued attribute irrespective of normal form always?
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From 1NF to BCNF, two relations are required. One with Primary key and all Single valued attributes and the other with the primary Key and all multi valued attributes.

In 4NF , there are relations for each multi valued attributes.

Ex.   A ia a Entity Set, with key a1 and a2,a3 are single valued attributes and mv1,mv2 are multi valued attributes.

      A( a1,a2,a3,mv1,mv2) 

Converting E-R to Relational Model, 

     A1(a1,a2,a3) and A2(a1,mv1,mv2)

In 4NF

    A1(a1,a2,a3) , A2(a1,mv1) and  A3(a1,mv2)

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yes .it is mandatory to create a separate table for every  multivalued attribute with primary in the current entity to avoid the heirarchy  in the table.
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Yes it is cumpolsary.

Every tablr needs to follow flat hierarchy that is what 1NF says. So if a table is not in 1NF then it cannot be in any other normal form.

CORRECT ME IF I AM WRONG.

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