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Beginning Database Design- P8:This book focuses on the relational database model from a beginning perspective. The title is, therefore, Beginning Database Design. A database is a repository for data. In other words, you can store lots of information in a database. A relational database is a special type of database using structures called tables. Tables are linked together using what are called relationships. You can build tables with relationships between those tables, not only to organize your data, but also to allow later retrieval of information from the database | Understanding Normalization Figure 4-37 shows a non-4NF transformation essentially only spreading the comma-delimited lists into separate records using the same existing EMPLOYEE table. i Employee i employee i skills i certifications NAME SKILLS CERTIFICATIONS Brad Programmer Sales MSCE Janet Sales Riffraff HTML Programmer Writing MSCE BSc Magenta Analyst DBA BSc OCP Columbia DBA Analyst Programmer HTML BSc OCP MSCE Spreading into multiple rows is a non-4th NF solution NOT a 4th NF Transform NAME SKILLS CERTIFICATIONS Brad Programer MSCE Brad Sales Janet Sales Riffraff HTML MSCE Riffraff Programmer BSc Riffraff Writing Magenta Analyst BSc Magenta DBA OCP Columbia DBA BSc Columbia Analyst OCP Columbia Programmer MSCE Columbia HTML Figure 4-37 An inelegant solution avoiding 4NF. 113 Chapter 4 Figure 4-38 performs a partial 4NF transformation by splitting skills and certifications from the EMPLOYEE table into SKILL and CERTIFICATION tables. This is only a partial transformation however because there are still many-to-many relationships between EMPLOYEE to SKILL tables and EMPLOYEE to certification tables. Employee employee NAME SKILLS CERTIFICATIONS Brad Programmer Sales MSCE Janet Sales Riffraff HTML Programmer Writing MSCE BSc Magenta Analyst DBA BSc OCP Columbia DBA Analyst Programmer HTML BSc OCP MSCE skills certifications Figure 4-38 A classic example 4NF using many-to-many relationships. 114 Understanding Normalization Figure 4-39 shows a more simplistic example where every FATHER table entry is unique because fathers can have multiple children but each child has only one father. Figure 4-39 A 4NF example using a one-to-many relationship. Figure 4-40 resolves the many-to-many relationships into EMPLOYEE_SKILL and EMPLOYEE_CERTIFI-CATION tables shown as many-to-many relationships in Figure 4-38. The many-to-many relationships resolved into one-to-many relationships in Figure 4-40 contain composites of employee names original skills and certifications arrays with
