Database Concepts (7th Edition)
7th Edition
ISBN: 9780133544626
Author: David M. Kroenke, David J. Auer
Publisher: PEARSON
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Expert Solution & Answer
Chapter 2, Problem 2.26RQ
Explanation of Solution
Meaning of the Equation:
The given expression is,
(D, E)->F
Explanation:
The meaning of the following equation is:
- Given the value for both D and E simultaneously, represented as composite (D, E), user can determine the value of F.
- If one of the values of D or E is not given, user cannot determine the value of F.
- The Composite (D, E) is the determinant of F.
- F is functionally dependent on the composite (D, E).
- It is a composite key.
Example:
- For a table Employee containing attributes ‘employee_id’, ‘employee_name’ and ‘employee_department’, it is observed that user can fill an online form asking to enter the ‘employee_name’ and ‘employee_department’ simultaneously and the
Database Management System (DBMS) searches the employee database and retrieves the information about employee id .
Therefore, expression can be (employee_name, employee_department) -> (employee-id)...
Expert Solution & Answer
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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 (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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