Top ten web hosting - id* lair_id name real name align 1 1
id* lair_id name real name align 1 1 Clean Freak John Smith Good 2 1 Soap Stud Efram Jones Good 3 2 The Dustmite Dustin Hare Evil id* zip_id lair address 1 45293 123 Poplar Avenue 2 45201 452 Elm Street #3D id* city st 45293 Townsburg OH 45201 Burgtown OH You may have noticed that you have created a many-to-many (M:N) relationship between the characters and their powers (a character can have multiple powers, and many characters may have the same power). There are two tables with primary keys, and a linking table between them has two foreign keys, one for each of the tables. The combination of the foreign keys is a primary key for the char_power table. This enables the M:N relationship. Just for fun, add a small table that links the superheroes to villains, and vice versa. This is another M:N relationship because any superhero can have multiple villain enemies, and any villain can have multiple superhero enemies. Of course, you have the character table as one of the many sides of the equation can you figure out what table to use for the other many side? If you said the character table, you are correct! This is just like the character-power relationship, but this time you reference the table to itself via a good_bad linking table. The goodguy_id and badguy_id columns each link to the id column in the character table. Each column in the good_bad table is a foreign key, and both columns make up a composite primary key. goodguy_id* badguy_id* 1 3 2 3 And just like that, you have created your database design. Congratulations! You now have a map that will help you create your database tables on the server. Not only that, but you just normalized your database design as well by modifying your database table structure so that dependencies make sense, and there is no redundant data. In fact, you have actually gone through the proper normalization steps of First, Second, and Third Normal Form. 282 Chapter 10
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