Example 4.4: A one-one relationship between entity sets E and F is repre- sented

Question

Example 4.4: A one-one relationship between entity sets E and F is repre- sented by arrows pointing to both E and F. For instance, Fig. 4.3 shows two entity sets, Studios and Presidents, and the relationship Runs between them attributes are omitted). We assume that a president can run only one studio and a studio has only one president, so this relationship is one-one, as indicated by the two arrows, one entering each entity set. RunsP R > residents Studios Figure 4.3: A one-one relationship Remember that the arrow means "at most one"; it does not guarantee ex Thus, in Fig. 4.3, we would expect that a "president" is surely associated with some studio; how could they be a istence of an entity of the set pointed to. "president" otherwise? However, a studio might not have a president at some particular time, so the arrow from Runs to Presidents truly means "at most one and not "exactly one." We shall discuss the distinction further in Section 4.3.3.

Explanation / Answer

Solution:

When the existence of the entity is confirmed then only we can combine these two entity sets in one.

Explanation:

The case will be when there is atleast one president for every studio and atleast one studio for every president, then the existence of the entity is confirmed.

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