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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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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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, computer-science and related others by exploring similar questions and additional content below.Similar questions
- What is the difference between disabling a constraint and dropping a constraint?arrow_forwardHow is adding a NOT NULL constraint to an existing table different from adding other types of constraints?arrow_forwardWhen must you define constraints at the table level rather than the column level?arrow_forward
- Which type of constraint can be used to make certain the category for a book is included when a new book is added to inventory?arrow_forwardWhat are referential constraint actions?arrow_forwardCreate a table named REP_CONTRACTS containing the columns listed in the following chart A composite PRIMARY KEY constraint including the Rep_ID, Store_ID, and Quarter columns should be assigned. In addition, FOREIGN KEY constraints should be assigned to both the Rep_ID and Store_ID columns.arrow_forward
- Problems 2932 are based on the following query: SELECT CUS_CODE, MAX(LINE_UNITSLINE_PRICE) FROM CUSTOMER NATURAL JOIN INVOICE NATURAL JOIN LINE WHERE CUS_AREACODE = '615' GROUP BY CUS_CODE; Assuming that you follow the recommendations you gave in Problem 29, how would you rewrite the query?arrow_forwardA table can have a maximum of how many PRIMARY KEY constraints?arrow_forwardYou’re creating a new table consisting of three columns: Col1, Col2, and Col3. Col1 should be the primary key and can’t have any NULL values, and each entry should be unique. Col3 must not contain any NULL values either. How many total constraints do you have to create? 1 2 3 4arrow_forward
- Which of the following is not a valid constraint type? a. PRIMARY KEYS b. UNIQUE c. CHECK d. FOREIGN KEYarrow_forwardWhich type of constraint should you use to ensure that every book has a profit margin between 15% and 25%?arrow_forwardWhat three join types are included in the outer join classification?arrow_forward
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