Oracle 12c: SQL
3rd Edition
ISBN: 9781305251038
Author: Joan Casteel
Publisher: Cengage Learning
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Chapter 4, Problem 1RQ
What is the difference between a PRIMARY KEY constraint and a UNIQUE constraint?
Expert Solution & Answer
Explanation of Solution
Difference between PRIMARY KEY and UNIQUE constraint
| PRIMARY KEY | UNIQUE |
| There will be only one primary key per table. | But in the case of unique constraint, there will be more than one unique constraint. |
| Primary key constraints are not nullable. | Unique key constraints are nullable. |
| When a primary key is defined, then a clustered index is automatically created. | When a unique key is defined, then a non-clustered index is generated. |
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Q4: Consider the following MAILORDER relational schema describing the data for a mail order
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PARTS(Pno, Pname, Qoh, Price, Olevel)
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ORDERS(Ono, Cno, Eno, Received, Shipped)
ODETAILS(Ono, Pno, Qty)
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d. Retrieve the names of customers who have ordered parts from employees living in Wichita.
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Chapter 4 Solutions
Oracle 12c: SQL
Ch. 4 - What is the difference between a PRIMARY KEY...Ch. 4 - How can you verify the constraints that exist for...Ch. 4 - A table can have a maximum of how many PRIMARY KEY...Ch. 4 - Which type of constraint can be used to make...Ch. 4 - Which type of constraint should you use to ensure...Ch. 4 - How is adding a NOT NULL constraint to an existing...Ch. 4 - When must you define constraints at the table...Ch. 4 - Prob. 8RQCh. 4 - What is the difference between disabling a...Ch. 4 - Prob. 10RQ
Ch. 4 - Prob. 1MCCh. 4 - Which of the following is not a valid constraint...Ch. 4 - Which of the following SQL statements is invalid...Ch. 4 - What is the maximum number of PRIMARY KEY...Ch. 4 - Prob. 5MCCh. 4 - How many NOT NULL constraints can be created at...Ch. 4 - The FOREIGN KEY constraint should be added to...Ch. 4 - What is the maximum number of columns you can...Ch. 4 - Which of the following commands can you use to...Ch. 4 - Prob. 10MCCh. 4 - In the initial creation of a table, if a UNIQUE...Ch. 4 - Which type of constraint should you use on a...Ch. 4 - Which of the following commands can be used to...Ch. 4 - Which of the following keywords allows the user to...Ch. 4 - Which of the following data dictionary objects...Ch. 4 - Which of the following types of constraints cant...Ch. 4 - Suppose you created a PRIMARY KEY constraint at...Ch. 4 - You’re creating a new table consisting of three...Ch. 4 - Which of the following types of restrictions can...Ch. 4 - Which of the following is the valid syntax for...Ch. 4 - Prob. 1HOACh. 4 - Prob. 2HOACh. 4 - Prob. 3HOACh. 4 - Add a column named Base_salary with a datatype of...Ch. 4 - Create a table named BOOK_STORES to include the...Ch. 4 - Add a constraint to make sure the Rep_ID value...Ch. 4 - Change the constraint created in Assignment #6 so...Ch. 4 - Create a table named REP_CONTRACTS containing the...Ch. 4 - Produce a list of information about all existing...Ch. 4 - Issue the commands to disable and then enable the...
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