DATABASE SYSTEM CONCEPTS (LOOSELEAF)
7th Edition
ISBN: 9781260515046
Author: SILBERSCHATZ
Publisher: MCG
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Chapter 6, Problem 5PE
Program Plan Intro
Entity-Relationship diagram:
- Entity-Relationship (ER) diagram is the method to represent the relational
database using graphical form. - This graphical representation shows only primary elements such as records, types, attributes, relationships between entities, and so on.
- The graphical representation of the ER diagram clearly describes the relationship among entities.
- In the diagram, every connector is labeled.
- On one side it is represented by the value 1, and on the other side it is labeled with the value “M”. This labeling is referred to as “cardinality constraint” of the relationship.
Explanation of Solution
b.
Graph has a cycle:
- If there is a cycle in the ER diagram means at least two pair of entity sets are related to each other in more than two distinct relations creating a loop...
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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 6 Solutions
DATABASE SYSTEM CONCEPTS (LOOSELEAF)
Ch. 6 - Prob. 1PECh. 6 -
Consider a database that includes the entity sets...Ch. 6 -
Design an E-R diagram for keeping track of the...Ch. 6 - Prob. 4PECh. 6 - Prob. 5PECh. 6 - Prob. 6PECh. 6 - Prob. 7PECh. 6 -
Consider a relation such as sec_course, generated...Ch. 6 -
Suppose the advisor relationship set were...Ch. 6 - Prob. 10PE
Ch. 6 - Prob. 11PECh. 6 - Prob. 12PECh. 6 - Prob. 13PECh. 6 - Prob. 14ECh. 6 - Prob. 15ECh. 6 - Prob. 16ECh. 6 - Prob. 17ECh. 6 -
Consider two entity sets A and B that both have...Ch. 6 - Prob. 19ECh. 6 - Prob. 20ECh. 6 - Prob. 21ECh. 6 - Prob. 22ECh. 6 - Prob. 23ECh. 6 -
Design a database for an airline. The database...Ch. 6 - Prob. 25ECh. 6 -
Design a generalization – specialization...Ch. 6 -
Explain the distinction between disjoint and...Ch. 6 -
Explain the distinction between total and partial...
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