Figure 10-22: 5NF can help to break down (Web site directory)
Tuesday, November 20th, 2007Figure 10-22: 5NF can help to break down composite primary keys. Does the end justify the means? Commercially, probably not! As you can see in Figure 10-22, the 5NF implementation starts to look a little like the hierarchical structure shown on the left of Figure 10-22. Case Study: Backtracking and Refining an OLTP Database Model This is the part where you get to ignore the deep-layer normalization applied in the previous section, and go back to the OLTP database model shown in Figure 10-18. And, yes, the database model in Figure 10-18 can be denormalized. Essentially, there are no rules or any kind of process with respect to performing denormalization. Denormalization is mostly common sense. In this case, common sense is the equivalent of experience. Figure 10-18 is repeated here again, in Figure 10-23, for convenience. 5NF Category_Primary primary secondary Category_Secondary primary (FK) secondary (FK) Category_Tertiary primary (FK) tertiary Primary_Secondary primary secondary Primary_Tertiary primary tertiary Secondary_Tertiary secondary tertiary 295 Creating and Refining Tables During the Design Phase
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