Database Concepts (8th Edition)
8th Edition
ISBN: 9780134601533
Author: David M. Kroenke, David J. Auer, Scott L. Vandenberg, Robert C. Yoder
Publisher: PEARSON
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Expert Solution & Answer
Chapter 2, Problem 2.15RQ
Explanation of Solution
Surrogate primary key:
- A system assigned primary key in a relational
database such as a serial number or any other which is not derived from any data in the database is known as surrogate primary key. - It is deputy of the primary key and will act as a primary key in the database and does not have any other significance.
- To simplify the primary key structures in the database, surrogate primary keys are created, and this ensures unique identification process in a relation.
Conditions to use the surrogate key:
The surrogate key for a relation is created when a primary key of a relation holds the below three conditions:
- If the relation has a composite primary key, then surrogate key should be created...
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Students have asked these similar questions
Consider the following database for some store:
Customers (cid, cname, city, discount)Agents (aid, aname, city, percent)Products (pid, pname, city, quantity, price)Orders (ordno, mon, cid, aid, pid, qty, dollars)
The relation Customers records the ID (cid), name (cname), location (city) of each customer and a discount percentage (discount) for this customer.
The relation Agents records the ID (aid), name (aname), location (city) of each agent and a transaction fee (percent) charged by this agent.
The relation Products lists the ID (pid), name (pname), location (city), quantity and price of available products.
And finally, the relation Orders contains a unique order number (ordno), the month (mon), customer (cid), agent (aid), product (pid), quantity (qty) of each order as well as the total value (dollars) of the transaction.
1. Express the following query in SQL
(a) List customers (names) who do not have discounts but purchased at least one product of price greater than $50.
(b) Find…
Consider the following relational schema and briefly answer the questions that follow:
Emp(eid: integer, ename: string, age: integer, salary: real)
Works(eid: integer, did: integer, pct_time: integer)
Dept(did: integer, budget: real, managerid: integer)
a. Define a table constraint on Dept that will ensure that all managers have age > 30.
b. Write SQL statements to delete all information about employees whose salaries exceed that of the manager of one or more departments that they work in. Be sure to ensure that all the relevant integrity constraints are satisfied after your updates.
Consider the following relations:
Student(snum: integer, sname: string, rmajor: string,
level: string, age: integer)
Class(cname: string, meets_at: time, room: string, fid: integer)
Enrolled(snum: integer, cname: string)
Faculty(fid: integer, fname: string, deptid: integer)
The meaning of these relations is straightforward; for example, Enrolled has one record per student-class pair such that the student is enrolled in the class.
2. Express each of the following integrity constraints in SQL unless it is implied by the primary and foreign key constraint; if so, explain how it is implied. If the constraint cannot be expressed in SQL, say so. For each constraint, state what operations (inserts, deletes, and updates on specific relations) must be monitored to enforce the constraint.
(a) Every faculty member must teach at least two courses.
(b) Every student must be enrolled in the course called 'Math101'.
(c) A student cannot add more than two courses at a time…
Chapter 2 Solutions
Database Concepts (8th 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 - Define the terms candidate key and primary key....Ch. 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 - Apply the normalization process to the Veterinary...
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