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System operating concepts concepts 944 mcgraw hill

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Unformatted text preview: primary key, used for joining tables together when querying the data. A primary key value must be unique with in the table (no two books can have the same ISBN number), and a primary key is also an index, which speeds up data retrieval based on the primary key. Now to define relationships between the Now tables tables Relationships Relationships Book_ Aut hor Ta bl e Boo k_ Subj e c t Ta bl e ISBN Author_ID 0072958863 1 ISBN Subject_ID 0072958863 2 0072958863 1 0471694665 1 0072958863 2 0471694665 2 0471694665 2 Second Normal Form Second As As the First Normal Form deals with redundancy of data across a horizontal row, Second Normal Form (or 2NF) deals with redundancy of data in vertical columns. As stated earlier, the normal forms are As progressive, so to achieve Second Normal Form, the tables must already be in First Normal Form. The Book Table will be used for the 2NF The example example 2NF Table 2NF Publ i s he r Ta bl e Publisher_ID Publisher Name 1 McGraw-Hill Book Ta bl e ISBN Title Pages Publisher_ID 0072958863 Database System Database Concepts Concepts 1168 1 0471694665 Operating System Operating Concepts Concepts 944 1 2NF 2NF Here Here we have a one-to-many relationship between the book table and the publisher. A book has only one publisher, and a publisher will publish many books. When we have a one-topublish many relationship, we place a foreign key in the many Book Table, pointing to the primary key of the Publisher Table. Publisher The other requirement for Second Normal Form The is that you cannot have any data in a table with a composite key that does not relate to all portions of the composite key. Third Normal Form Third Third Third normal form (3NF) requires that there are no functional dependencies of non-key attributes on something other than a candidate key. A table is in 3NF if all of the non-primary table key attributes are mutually independent There should not be transitive There dependencies Boyce-Codd Normal Form Boyce-Codd BCNF BCNF requires that the table is 3NF and only determinants are the candidate keys only END END...
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