# Question

Explain the difference between a weak and a strong entity set.

## Answer to relevant Questions

We can convert any weak entity set to a strong entity set by simply adding appropriate attributes.Why, then, do we have weak entity sets?An E-R diagram can be viewed as a graph. What do the following mean in terms of the structure of an enterprise schema?a. The graph is disconnected.b. The graph is acyclic.Explain the distinction between total and partial constraints. In Chapter we saw how to represent many-to-many, many-to-one, one-tomany, and one-to-one relationship sets. Explain how primary keys help us to represent such relationship sets in the relational model.Let the following relation schemas be given: R = (A, B, C) S = (D, E, F) Let relations r(R) and s(S) be given. Give an expression in the tuple relational calculus that is equivalent to each of the following: a. II ...Post your question

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