June 2010
Intermediate to advanced
328 pages
7h 51m
English
The Scarecrow in The Wizard of Oz gives Dorothy uncertain directions when she asks which fork in the road she should take to get to the Emerald City. What should be a clear answer to Dorothy’s simple question just confuses her when the Scarecrow tries to give her two answers at once.

This kind of association is illustrated in the entity-relationship diagram in Figure 12, Polymorphic association. The foreign key in the child table “forks,” so a row in the Comments table matches either a row in the Bugs table or a row in the FeatureRequests table. The curved arc in the diagram ...
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