entity relationship - Maximum number of tuples in this relation R , ER model? -


er diagram

answer given : 1000

i don't understand side it's many-one relation , side it's one-one relation.

there many er diagramming conventions, , haven't explained or given reference yours. included expressing cardinalities, , in particular cardinalities n-ary relationships n > 2.

googling text of question: diagram appears in (different) question in this solution says of diagram:

(i) unique pair (a,b) there can unique value of c in relationship set r , and
(ii) unique pair (a,c) there can unique value of b in r .

so seems arrow indicates target entity appears once a given appearance of combination of others in relationship set.

there's @ 1 c per (a,b) pair; every {a,b} pair unique in set. there @ 10*100 entities.

there's @ 1 b per (a,c) pair; every {a,c} pair unique in set. there @ 10*1000 entities.

from both those, know there @ 1000 entities.

there 10*100 entities, since each possible (a,b) pair appear in set each different c without violating cardinality constraints. maximum number of entities not smaller 1000.

so maximum number of associative entity triples in relationship set 1000.

i don't understand side it's many-one relation , side it's one-one relation.

notice there aren't "sides" n-ary relationship n > 2. there sides each binary relationship between entity type participating in role , (n-1)-tuples combined entitity types participating in other roles. report cardinality each side of each role's binary relationship.


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