Beginning Oracle Database 11g Administration From Novice to Professional

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CHAPTER 7 PHYSICAL DATABASE DESIGN
the availability of the rest of the data in the table. Global indexes are most suitable when
the query does not specify the partitioning criterion. A global index may or may not be
partitioned and can even have a different partition scheme than its table.
Denormalization and Materialized Views
Denormalization is a technique that is used to improve the efficiency of Join operations.
Consider the and tables from the order management database described
in Oracle Database 11g Java Developer’s Guide. To avoid having to join these tables, we
could replace them with a table that contains all the data items from both tables. This
eliminates the need to join the two tables frequently, but it introduces its own set of problems.
Observe that data items such as , , , and must now be
duplicated if there is more than one line in an order; if any of these data items needs to
be changed, multiple data rows will have to be updated. The duplication of data thus creates
the possibility that mistakes will be made.
Materialized views can be used to avoid the problems created by denormalization.
Instead of replacing the and tables with a denormalized table, we could
prejoin the tables and store the results in a structure called a materialized view, as illustrated
in Listing 7-8.
Listing 7-8. Example of a Materialized View