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SQL allows a foreign-key dependency to refer to the same relation, as in the following example: create table manager (employee name char(20), manager name char(20), primary key employee_name, foreign key (manager name) references manager on delete cascade) Here, employee name is a key to the table manager, meaning that each em- ployee has at most one manager. The foreign-key clause requires that every manager also be an employee. Explain exactly what happens when a tuple in the relation manager is deleted.

SQL allows a foreign-key dependency to refer to the same relation, as in the following example: create table manager (employee name char(20), manager name char(20), primary key employee_name, foreign key (manager name) references manager on delete cascade) Here, employee name is a key to the table manager, meaning that each em- ployee has at most one manager. The foreign-key clause requires that every manager also be an employee. Explain exactly what happens when a tuple in the relation manager is deleted.

Computer Networking: A Top-Down Approach (7th Edition)
Computer Networking: A Top-Down Approach (7th Edition)
7th Edition
ISBN:9780133594140
Author:James Kurose, Keith Ross
Publisher:James Kurose, Keith Ross
Chapter1: Computer Networks And The Internet
Section: Chapter Questions
Problem R1RQ: What is the difference between a host and an end system? List several different types of end...
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SQL allows a foreign-key dependency to refer to the same relation, as in the following example: create table manager (employee name char(20), manager name char(20), primary key employee_name, foreign key (manager name) references manager on delete cascade) Here, employee name is a key to the table manager, meaning that each em- ployee has at most one manager. The foreign-key clause requires that every manager also be an employee. Explain exactly what happens when a tuple in the relation manager is deleted.
Transcribed Image Text:SQL allows a foreign-key dependency to refer to the same relation, as in the following example: create table manager (employee name char(20), manager name char(20), primary key employee_name, foreign key (manager name) references manager on delete cascade) Here, employee name is a key to the table manager, meaning that each em- ployee has at most one manager. The foreign-key clause requires that every manager also be an employee. Explain exactly what happens when a tuple in the relation manager is deleted.
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