n-m-k
ternary relationship (many-to-many-to-many ternary relationship)
In the above ER diagram, the cardinality ratio is
n:m:k. One supplier can supply for one project many parts. The same part can be
supplied by one supplier for many projects. The same part can be supplied for
one project by many suppliers.
Note: In all ternary relationships, the middle diamond
relationship can have attribute(s) when those attribute(s) cannot be directly
assigned to the entities as has been explained in case of many-many binary
relationships.
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