We began by looking at Visio 2010. We drug an Entity onto the grid and use the properties window to Name it DVD. Then we assigned a primary Key and some fields. We Determined that actor was a multi-valued attribute, meaning that every DVD probably has many Actors, so we broke it into its own entity.
There are Three Kinds of relationships:
*One to One, where each record in the primary key is related to no more than 1 record in the child table
*One to Many, where each record in the primary key table can be related to zero or several records in the child table
*Many To Many, where each record in the primary key table can be related to any number of records in the child table, and each record in the child table can be related to any number of records in the parent table. These must be resolved by adding a linking table
Next we determined that there is a many to many relationship between DVD and Actor.Here is the Diagram
No comments:
Post a Comment