This chapter stressed the importance of data normalization when constructing a relational database. Why then is it important to de-normalize data in a data warehouse?
What will be an ideal response?
Wherever possible, normalized tables pertaining to selected events should be consolidated into de-normalized tables. Because of the vast size of a data warehouse, inefficiency caused by joining normalized data can be very detrimental to the performance of the system. A three-way join between tables in a large data warehouse may take an unacceptably long time to complete and may be unnecessary. Since historical data are static in nature, nothing is gained by constructing normalized tables with dynamic links.
PTS: 1
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A. compressed audio B. MIDI C. compressed data D. CD-DA
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George is developing an XSLT style sheet to display data from research surveys. The structure of the surveys.xml file is shown in the accompanying figure. He comes to you for assistance in preparing the final file.?
?The source document contains data for thousands of surveys. George would like to display information for only the first six surveys. Which of the following shows the correct syntax for the predicate George should use to insure only the first six surveys are displayed?
A. ?[position() <= 5] B. ?[position() = 5] C. ?[position() <= 5] D. ?[position() < 6]
Which operation will retrieve the item at position i in anArray?
A. anArray[i] = val; B. val[i] = anArray[i]; C. val = anArray[i]; D. i[val] = anArray;