Oracle 12c: SQL
Oracle 12c: SQL
3rd Edition
ISBN: 9781305251038
Author: Joan Casteel
Publisher: Cengage Learning
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Chapter 4, Problem 1MC
Program Description Answer

None of the given statements” is a correct statement.

Hence, correct answer is option “D”.

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Which of the following statements is correct? ( refer to the tables in the JustLee Books database).                                                                                   a. A PRIMARY KEY constraint allows NULL values in the primary key column(s).                                                                                                              b. You can enable a dropped constraint if you need it in the future. c. Every table must have at least one PRIMARY KEY constraint, or Oracle 12                  c doesn’t allow the table to be created.                                                            d. None of the above statements is correct
Which of the following fields also serves as a primary key in another table when two tables are joined together on that value? a. foreign key b. primary key c. turn key d. repeating group key
9. Write a trigger that prohibits duplicate values except for nulls in the NoDupName column of the following table: CREATE TABLE TestUniqueNulls (RowID NoDupName varchar(20) int IDENTITY NOT NULL, NULL); (Note that you can’t do this by using a unique constraint because the constraint wouldn’t allow duplicate null values.) If an INSERT or UPDATE statement creates a duplicate value, roll back the statement and return an error message. Write a series of INSERT statements that tests that duplicate null values are allowed but duplicates of other values are not.

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Oracle 12c: SQL

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