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databases Online Quiz - 112

Description: databases Online Quiz - 112
Number of Questions: 20
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Tags: databases
Attempted 0/20 Correct 0 Score 0
  1. Data Item

  2. Record Occurence

  3. Record

  4. Record Type


Correct Option: D

"Pages" contain

  1. Areas

  2. Record Occurence

  3. Record Type

  4. Data Item


Correct Option: B

A "page" can have multiple record-occurences

  1. True

  2. False


Correct Option: A

Which two statements about views are true? (Choose two.)

  1. A view can be created as read only.

  2. A view can be created as a join on two or more tables. AND Insert and delete operations cannot be performed on views using functions

  3. A view cannot have an ORDER BY clause in the SELECT statement.

  4. A view cannot be created with a GROUP BY clause in the SELECT statement.


Correct Option: A,B,C,D

In which case would you use a FULL OUTER JOIN?

  1. Both tables have NULL values.

  2. You want all unmatched data from one table.

  3. You want all matched data from both tables.

  4. You want all unmatched data from both tables.

  5. One of the tables has more data than the other.


Correct Option: D

Difference between Truncate and Delete

  1. TRUNCATE is a DDL command whereas DELETE is a DML command

  2. TRUNCATE is much faster than DELETE

  3. In case of TRUNCATE ,Trigger doesn't get fired.But in DML commands like DELETE .Trigger get fired

  4. All of the above


Correct Option: A

AI Explanation

To answer this question, let's go through each option to understand why it is correct or incorrect:

Option A) TRUNCATE is a DDL command whereas DELETE is a DML command - This option is correct. TRUNCATE is a Data Definition Language (DDL) command used to delete all the rows from a table, while DELETE is a Data Manipulation Language (DML) command used to delete specific rows from a table.

Option B) TRUNCATE is much faster than DELETE - This option is partially correct. TRUNCATE is generally faster than DELETE because it does not generate any transaction logs and does not need to record individual row deletions. However, the exact performance difference may vary depending on the specific database system and the size of the table.

Option C) In case of TRUNCATE, Trigger doesn't get fired. But in DML commands like DELETE, Trigger gets fired - This option is correct. When you use TRUNCATE, triggers associated with the table are not fired. However, when you use DELETE, triggers associated with the table may get fired.

Option D) All of the above - This option is incorrect. The correct answer is A, as explained above.

The correct answer is A. TRUNCATE is a DDL command whereas DELETE is a DML command.

Difference between Truncate and Delete(select multiple answers)

  1. TRUNCATE is a DDL command whereas DELETE is a DML command

  2. TRUNCATE is much faster than DELETE

  3. In case of TRUNCATE ,Trigger doesn't get fired.But in DML commands like DELETE .Trigger get fired

  4. All of the above


Correct Option: A

Which data dictionary table should you query to view the object privileges granted to the user on specific columns?

  1. USER_TAB_PRIVS_MADE

  2. USER_TAB_PRIVS_RECD

  3. USER_COL_PRIVS_MADE

  4. USER_COL_PRIVS_RECD


Correct Option: D

Which of the following are the valid ordering sequences of an ORDER BY clause?

  1. A. ASEC

  2. B. DESC

  3. C. REVERT

  4. D. ASC

  5. Both B and D

  6. Both A and B


Correct Option: E

Which clause should you use to restrict group results

  1. WHERE

  2. HAVING

  3. RESTRICT

  4. ORDER BY

  5. GROUP BY

  6. Both A and B


Correct Option: B

Merge Syntax

  1. A. MERGE INTO <> USING <> WHEN MATCHED THEN UPDATE ------ WHEN NOT MATCHED THEN INSERT -------

  2. B. MERGE <> USING <> WHEN MATCHED THEN UPDATE ------ WHEN NOT MATCHED THEN INSERT -------

  3. C. MERGE INTO <> USING <> WHEN EXISTS THEN UPDATE ------

  4. D. MERGE INTO <> USING <> WHEN NOT MATCHED THEN INSERT ------

  5. Both A and D


Correct Option: A

Which two statements about sequences are true?

  1. A. You use a NEXTVAL pseudo column to look at the next possible value that would be generated from a sequence, without actually retrieving the value

  2. B. You use a CURRVAL pseudo column to look at the current value just Generated from a sequence, without affecting the further values to be generated from the sequence.

  3. You use a NEXTVAL pseudo column to obtain the next possible value from a sequence by actually retrieving the value from the sequence

  4. Both A and B


Correct Option: D
Explanation:

To answer this question, we need to understand the concepts of sequences in the context of databases.

A sequence is an object in a database that generates a sequence of unique values. In Oracle, two pseudo columns are used in conjunction with sequences: NEXTVAL and CURRVAL.

Statement A: You use a NEXTVAL pseudo column to look at the next possible value that would be generated from a sequence, without actually retrieving the value. This statement is true. The NEXTVAL pseudo column allows you to obtain the next possible value from a sequence without affecting the further values to be generated. It effectively increments the sequence by 1 and returns the next value.

Statement B: You use a CURRVAL pseudo column to look at the current value just generated from a sequence, without affecting the further values to be generated from the sequence. This statement is also true. The CURRVAL pseudo column allows you to obtain the current value generated from a sequence without affecting the further values to be generated. It does not increment the sequence; it only returns the current value.

Statement C: You use a NEXTVAL pseudo column to obtain the next possible value from a sequence by actually retrieving the value from the sequence. This statement is incorrect. The NEXTVAL pseudo column does not retrieve the value from the sequence; it only returns the next possible value without affecting the sequence.

Therefore, the correct answer is option D: Both A and B. Both statements A and B correctly describe the usage of NEXTVAL and CURRVAL pseudo columns in relation to sequences in Oracle databases.

You need to perform certain data manipulation operations through a view called EMP_DEPT_VU, which you previously created. You want to look at the definition of the view (the SELECT statement on which the view was create.) How do you obtain the definition of the view?

  1. Use the DESCRIBE command in the EMP_DEPT VU view.

  2. Use the DEFINE VIEW command on the EMP_DEPT VU view

  3. Use the DESCRIBE VIEW command on the EMP_DEPT VU view

  4. Query the USER_VIEWS data dictionary view to search for the EMP_DEPT_VU view


Correct Option: D

AI Explanation

To obtain the definition of a view, you can query the data dictionary view called USER_VIEWS. This view contains information about all the views owned by the current user.

Option A) Using the DESCRIBE command in the EMP_DEPT_VU view is incorrect. The DESCRIBE command is used to display the structure of a table, not a view.

Option B) Using the DEFINE VIEW command on the EMP_DEPT_VU view is incorrect. The DEFINE VIEW command is not a valid command in most database systems. It is not used to obtain the definition of a view.

Option C) Using the DESCRIBE VIEW command on the EMP_DEPT_VU view is incorrect. The DESCRIBE VIEW command is not a valid command in most database systems. It is not used to obtain the definition of a view.

Option D) Querying the USER_VIEWS data dictionary view to search for the EMP_DEPT_VU view is correct. The USER_VIEWS view contains information about all the views owned by the current user, including their definitions.

Therefore, the correct answer is D) Query the USER_VIEWS data dictionary view to search for the EMP_DEPT_VU view.

For which two constraints does the Oracle Server implicitly create a unique index?

  1. NOT NULL and PRIMARY KEY

  2. PRIMARY KEY and UNIQUE key

  3. FOREIGN KEY and PRIMARY KEY

  4. CHECK

  5. UNIQUE


Correct Option: B

SELECT ROUND(TRUNC(MOD(1600,10),-1),2) FROM dual; What will be displayed?

  1. 0

  2. NULL

  3. 0.1

  4. NA


Correct Option: A
Explanation:

To solve this question, the user needs to understand the functions used in the SQL query:

  • MOD: returns the remainder of a division operation
  • TRUNC: truncates a number to a specified number of decimal places
  • ROUND: rounds a number to a specified number of decimal places

Now, let's evaluate the given query step by step:

  • MOD(1600,10) returns the remainder of 1600 divided by 10, which is 0.
  • TRUNC(0,-1) truncates 0 to the nearest 10th place, which is still 0.
  • ROUND(0,2) rounds 0 to 2 decimal places, resulting in 0.

Therefore, the correct answer is:

The Answer is: A. 0

You created a view called EMP_DEPT_VU that contains three columns from the EMPLOYEES and DEPARTMENTS tables: EMPLOYEE_ID, EMPLOYEE_NAME AND DEPARTMENT_NAME. The DEPARTMENT_ID column of the EMPLOYEES table is the foreign key to the primary key DEPARTMENT_ID column of the DEPARTMENTS table. You want to modify the view by adding a fourth column, MANAGER_ID of NUMBER data type from the EMPLOYEES tables. How can you accomplish this task?

  1. ALTER VIEW emp_dept_vu (ADD manager_id NUMBER);

  2. MODIFY VIEW emp_dept_vu (ADD manager_id NUMBER);

  3. ALTER VIEW emp_dept_vu AS SELECT employee_id, employee_name, department_name, manager_id FROM employee e, departments d WHERE e.department_id = d.department_id;

  4. CREATE OR REPLACE VIEW emp_dept_vu AS SELECT employee_id, employee_name, department_name, manager_id FROM employees e, departments d WHERE e.department_id = d.department_id;


Correct Option: D

AI Explanation

To modify the view by adding a fourth column, MANAGER_ID, from the EMPLOYEES table, you need to use the CREATE OR REPLACE VIEW statement.

The correct answer is:

D. CREATE OR REPLACE VIEW emp_dept_vu AS SELECT employee_id, employee_name, department_name, manager_id FROM employees e, departments d WHERE e.department_id = d.department_id;

Explanation: Option A) ALTER VIEW emp_dept_vu (ADD manager_id NUMBER); - This option is incorrect because the ALTER VIEW statement does not have an ADD clause to add columns to an existing view.

Option B) MODIFY VIEW emp_dept_vu (ADD manager_id NUMBER); - This option is incorrect because there is no MODIFY VIEW statement in SQL to modify the structure of a view.

Option C) ALTER VIEW emp_dept_vu AS SELECT employee_id, employee_name, department_name, manager_id FROM employee e, departments d WHERE e.department_id = d.department_id; - This option is incorrect because the ALTER VIEW statement does not allow you to change the SELECT statement of the view.

Option D) CREATE OR REPLACE VIEW emp_dept_vu AS SELECT employee_id, employee_name, department_name, manager_id FROM employees e, departments d WHERE e.department_id = d.department_id; - This option is correct because the CREATE OR REPLACE VIEW statement allows you to create or modify a view. In this case, it creates a view called emp_dept_vu with the specified columns and queries the EMPLOYEES and DEPARTMENTS tables to retrieve the required data.

Therefore, the correct answer is option D.

In ISQL plus how to see errorsof a plsql code

  1. A.SHOW ERRORS

  2. B. Query the USER_ERRORS data dictionary view

  3. Both A and B

  4. None of the above


Correct Option: C

Bit map Vs B-tree indexes

    1. Bit map indexes are used on low-cardinality columns(having low distinct values) 2.B-tree indexes are most effective for high-cardinality data(only for unique columns)
  1. B-tree indexes cannot be used in environments typically have large amounts of data and ad hoc queries

  2. bitmap indexes can be created on partitioned tables

  3. All of the above


Correct Option: D

Syntax of Cursor declaration: Cursor <> as select * from <>;

  1. True

  2. False


Correct Option: B

Which of the following is not a schema object :

  1. Indexes

  2. tables

  3. public synonyms

  4. triggers

  5. packages


Correct Option: C
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