a. What is a trigger? How can triggers be used to enforce required children?
b. Explain why the enforcement of M-M relationships is particularly difficult.
c. Explain the need for each of the design decisions in Figure 6-33.
![412_0db2aba0-c735-45cd-b8c4-b3d15975af44.png](https://secure.tutorsglobe.com/CMSImages/412_0db2aba0-c735-45cd-b8c4-b3d15975af44.png)
d. Explain the implications of each of the minimum cardinality specifications in Figure 6-38.
![1238_79101262-fef1-4c6b-839c-81f2feed2f43.png](https://secure.tutorsglobe.com/CMSImages/1238_79101262-fef1-4c6b-839c-81f2feed2f43.png)
e. Explain the rationale for each of the entries in the table in Figure 6-40.
![336_d7c0d03f-8516-4e30-b159-a76e5f1c6a8e.png](https://secure.tutorsglobe.com/CMSImages/336_d7c0d03f-8516-4e30-b159-a76e5f1c6a8e.png)