What restrictions apply to the use of the aggregate functions within the SELECT statement? How do nulls
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Question:
- What restrictions apply to the use of the aggregate functions within the SELECT statement? How do nulls affect the aggregate functions?
- What is the difference between a subquery and a join? Under what circumstances would you not be able to use a subquery?
- What is the result of an attempt to add, subtract, multiply, or divide two number fields, one of which contains a null value?
- Explai why the two following commands produce different results.
SELECT DISTINCT COUNT (V_CODE) FROM PRODUCT;
SELECT COUNT (DISTINCT V_CODE) FROM PRODUCT;
- Considerthe relation instanceEXAM (Student, Subject, Rank). Themeaningofan
EXAM tupleis that aspecified student examined in aspecified subject achieves a specified rank in the class. Further, no two students obtain thesame rank inthesame subject.
EXM
Student | Subject | Rank |
McGrady | Math | 3 |
Howard | Math | 4 |
McGrady | English | 2 |
Jackson | English | 1 |
Yao | Math | 1 |
Yao | Chemistry | 1 |
Sura | Math | 2 |
Ward | English | 3 |
Taylor | Chemistry | 2 |
Taylor | Math | 5 |
Ewing | Chemistry | 3 |
Figure 1
What is (are)thecandidatekey(s)ofEXAM? Based onyourprimarykey,what normal form violations existin EXAM?
Related Book For
Database Systems A Practical Approach to Design Implementation and Management
ISBN: 978-0132943260
6th Edition Global
Authors: Thomas Connolly, Carolyn Begg
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