Normalization provides benefits by avoiding storage of redundant data. Storing the
department in every employee record not only would waste space but also would
lead to a data maintenance issue. If the department name changed, you would have
to update every employee record, even though no employees had actually changed
departments. By normalizing the department data into a table and simply pointing to
the appropriate row from the employee rows, youavoid both duplication of data and
this type of problem.
Normalization also reduces the amount of data that any one row in a table contains.
The less data in a row, the less I/O is needed to retrieve it, which helps to avoid this
performance bottleneck. In addition, the smaller the size of a row, the more rows are
retrieved per data block, which increases the likelihood that more than one desired
row will be retrieved in a single I/O operation. And the smaller the row, the more
rows will be kept in Oracle??™s system buffers, which also increases the likelihood that
a row will be available in memory when it??™s needed, thereby avoiding the need for
any disk I/O at all.
Pages:
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243