Database Concepts (7th Edition)
7th Edition
ISBN: 9780133544626
Author: David M. Kroenke, David J. Auer
Publisher: PEARSON
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Textbook Question
Chapter 2, Problem 2.21RQ
Explain three possible interpretations of a null value.
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Chapter 2 Solutions
Database Concepts (7th Edition)
Ch. 2 - Prob. 2.1RQCh. 2 - Define the term entity, and give an example of an...Ch. 2 - Prob. 2.3RQCh. 2 - Prob. 2.4RQCh. 2 - Prob. 2.5RQCh. 2 - Prob. 2.6RQCh. 2 - Prob. 2.7RQCh. 2 - Prob. 2.8RQCh. 2 - Prob. 2.9RQCh. 2 - Define the term unique key and give an example.
Ch. 2 - Prob. 2.11RQCh. 2 - Prob. 2.12RQCh. 2 - Prob. 2.13RQCh. 2 - Describe four uses of a primary key.Ch. 2 - Prob. 2.15RQCh. 2 - Prob. 2.16RQCh. 2 - Prob. 2.17RQCh. 2 - Explain the term foreign key, and give an example.Ch. 2 - Prob. 2.19RQCh. 2 - Prob. 2.20RQCh. 2 - Explain three possible interpretations of a null...Ch. 2 - Give an example of a null value (other than one...Ch. 2 - Prob. 2.23RQCh. 2 - Prob. 2.24RQCh. 2 - Prob. 2.25RQCh. 2 - Prob. 2.26RQCh. 2 - Prob. 2.27RQCh. 2 - Define the term primary key in terms of functional...Ch. 2 - Prob. 2.31RQCh. 2 - Examine the data in the Veterinary Office...Ch. 2 - Prob. 2.33RQCh. 2 - Describe a modification problem that occurs when...Ch. 2 - Prob. 2.35RQCh. 2 - Prob. 2.36RQCh. 2 - Prob. 2.37RQCh. 2 - Apply the normalization process to the Veterinary...Ch. 2 - Prob. 2.39ECh. 2 - Prob. 2.40E
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- What are nulls? Which field cannot accept null values? Why?arrow_forwardConsider a scenario in which the SQL statement is of the form SELECT DISTINCT c1, c2, c3 from T. Why might it make sense to create an index to optimize this query?arrow_forwardJustify your use of EXISTS and associated subqueries.arrow_forward
- This is a computer science question relating to SQL: Write out a scenario where: -You would constrain and validate user input to prevent a SQL injection attack. Explain what the input is, and write the code snippet showing how you validated it.arrow_forwardIn what sense do nulls not exist? Invalid values are not allowed in what kind of field? Why?arrow_forwardHow does the SQL ORDER BY clause work, and why might it be important when using database functions like MAX() or MIN()? Provide a query illustrating its usage.arrow_forward
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