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databases Online Quiz - 142

Description: databases Online Quiz - 142
Number of Questions: 20
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Tags: databases
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What is true about triggers I. instead of trigger can be used on tables and views 2. instead of trigger can fire at eah row and statement levels. 3. Compund trigger in 10g allows us to specify multiple timig events on single database objects. 4. we should not use the same object which fired the trigger inside the trigger. this will result in mutating trigger error.

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  1. 2 and 4 are true

  2. 1 , 3 and 4 are true

  3. 1 and 3 are true

  4. Only 4 is true

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Correct Option: D

For which constraints are indexes created when the constraint is added?
technology databases

  1. Check

  2. Unique

  3. Primary key

  4. not null

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Correct Option: B,C

What is the difference between Union and Union all statements

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  1. Union all used for combining multiples queries using single union all

  2. There is no difference

  3. the union will eliminate duplicate records in result set but, union all will print the duplicate records

  4. Union all is used for select with multiple columns

Show answer
Correct Option: C

what is true about Delete and truncate 1. Truncate can not be used in PL/SQL 2. Delete will remove the data and will not move watermark. 3. Both statements require commit 4. truncate can remove selected records

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  1. 1 and 2 are correct

  2. All are true

  3. 1,2 and 3 are correct

  4. 2,3 and 4 are correct

Show answer
Correct Option: A

What is the default value for the OPTIMIZER_MODE initialization parameter?
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  1. FIRST_ROWS

  2. ALL_ROWS

  3. CHOOSE

  4. COST

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Correct Option: C

Can we have multiple primary keys in a table?
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  1. True

  2. False

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Correct Option: B

Which are the aggregate functions?

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  1. SUM

  2. AVG

  3. trim

  4. median

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Correct Option: A,B,D

We have unique constraint on sal column on emp table. can the column accept multiple null values?

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  1. True

  2. False

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Correct Option: A

Can we have multiple check constraints on a single column of a table.
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  1. True

  2. False

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Correct Option: A

We can view the constraint details from following data dictionary views
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  1. user_constraints

  2. user_tables

  3. user_cons_columns

  4. all_tab_cols

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Correct Option: A,C

Comparision of Decode and case statement

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  1. Both are same

  2. case can check for non equality operator but decode checks for equality operator

  3. decode can be used for comparing value of one variable/condition. but case can check for multiple conditions

  4. case can not be used in where clause. but decode can be used.

Show answer
Correct Option: B,C

Evaluate the SQL statement: SELECT ROUND(45.953, -1), TRUNC(45.936, 2) FROM dual; Which values are displayed?

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  1. 46 and 45

  2. 46 and 45.93

  3. 50 and 45.93

  4. 50 and 45.9

Show answer
Correct Option: C

Which are DML statements? (Choose all that apply.)

technology databases

  1. COMMIT

  2. MERGE

  3. UPDATE

  4. DELETE

  5. CREATE

  6. DROP

Show answer
Correct Option: B,C,D

AI Explanation

To answer this question, we need to understand what DML (Data Manipulation Language) statements are. DML statements are used to manipulate data stored in a database. They include operations such as inserting, updating, deleting, and merging data.

Let's go through each option to determine which ones are DML statements:

Option A) COMMIT - This option is not a DML statement. COMMIT is used to save the changes made to the database since the last COMMIT or ROLLBACK statement. It is a transaction control statement.

Option B) MERGE - This option is a DML statement. The MERGE statement combines insert, update, and delete operations into one statement. It is used to perform conditional updates or inserts based on a specified condition.

Option C) UPDATE - This option is a DML statement. The UPDATE statement is used to modify existing data in a table.

Option D) DELETE - This option is a DML statement. The DELETE statement is used to remove existing data from a table.

Option E) CREATE - This option is not a DML statement. CREATE is a Data Definition Language (DDL) statement used to create database objects such as tables, views, or indexes.

Option F) DROP - This option is not a DML statement. DROP is a DDL statement used to remove database objects such as tables or views.

Based on the explanations above, the correct answers are B) MERGE, C) UPDATE, and D) DELETE. These options are DML statements as they involve manipulating data in a database.

On which line will the following command fail? INSERT INTO plsql101_product ( product_name, product_price, quantity_on_hand, last_stock_date ) VALUES ( 'New Product', 1.95, 10, TO_CHAR(USER) ) ;

technology databases

  1. 1

  2. 2

  3. 7

  4. 10

Show answer
Correct Option: D

Evaluate the set of SQL statements: CREATE TABLE dept (deptno NUMBER(2), dname VARCHAR2(14), loc VARCHAR2(13)); ROLLBACK; DESCRIBE DEPT What is true about the set? A. The DESCRIBE DEPT statement displays the structure of the DEPT table. B. The ROLLBACK statement frees the storage space occupied by the DEPT table. C. The DESCRIBE DEPT statement returns an error ORA-04043: object DEPT does not exist. D. The DESCRIBE DEPT statement displays the structure of the DEPT table only if there is a COMMIT statement introduced before the ROLLBACK statement.

technology databases

  1. A

  2. B

  3. C

  4. D

Show answer
Correct Option: A
Explanation:

To understand the given set of SQL statements, the user must have knowledge of SQL commands and their functions.

  • CREATE TABLE statement creates a table with the specified columns and data types.

  • ROLLBACK statement rolls back the current transaction and undoes all the changes, freeing the storage space occupied by the table.

  • DESCRIBE statement displays the structure of the specified table.

Now, let's evaluate each option:

A. The DESCRIBE DEPT statement displays the structure of the DEPT table.

This option is correct. The DESCRIBE statement is used to display the structure of the specified table, and in this case, the specified table is DEPT. So, the DESCRIBE DEPT statement will display the structure of the DEPT table.

B. The ROLLBACK statement frees the storage space occupied by the DEPT table.

This option is incorrect. The ROLLBACK statement rolls back the current transaction and undoes all the changes, but it does not free the storage space occupied by the DEPT table. The table will still exist even after the ROLLBACK statement is executed.

C. The DESCRIBE DEPT statement returns an error ORA-04043: object DEPT does not exist.

This option is incorrect. The DEPT table was created using the CREATE TABLE statement, so it exists in the database. The DESCRIBE DEPT statement will display the structure of the DEPT table.

D. The DESCRIBE DEPT statement displays the structure of the DEPT table only if there is a COMMIT statement introduced before the ROLLBACK statement.

This option is incorrect. The DESCRIBE statement displays the structure of the specified table regardless of the presence of a COMMIT statement. The ROLLBACK statement undoes all the changes made in the current transaction, but it does not affect the execution of the DESCRIBE statement.

Therefore, the correct answer is:

The Answer is: A. A

Among these Which are the system variables

technology databases

  1. SYSDATE

  2. USER

  3. USERENV

  4. ALL THE ABOVE

Show answer
Correct Option: D

What would be the result of the following DECODE function? DECODE(‘B’, ‘A’, ‘One’, ‘E’, ‘Five’, ‘I’, ‘Nine’, ‘O’, ‘Fifteen’, ‘U’, ‘Twenty-one’, ‘N/A’ )

technology databases

  1. One

  2. N/A

  3. Two

  4. Five

Show answer
Correct Option: B

AI Explanation

To answer this question, we need to understand how the DECODE function works.

The DECODE function in SQL is used to perform conditional logic within a query. It takes multiple pairs of values and returns a result based on the comparison of an expression with each pair.

In the given DECODE function:

DECODE('B', 'A', 'One', 'E', 'Five', 'I', 'Nine', 'O', 'Fifteen', 'U', 'Twenty-one', 'N/A')

The expression being compared is 'B'.

The DECODE function compares the expression 'B' with each pair of values. If the expression 'B' matches the first value of a pair, then the function returns the second value of that pair.

Let's go through each pair:

  1. ('A', 'One'): The expression 'B' does not match 'A', so this pair is not considered.
  2. ('E', 'Five'): The expression 'B' does not match 'E', so this pair is not considered.
  3. ('I', 'Nine'): The expression 'B' does not match 'I', so this pair is not considered.
  4. ('O', 'Fifteen'): The expression 'B' does not match 'O', so this pair is not considered.
  5. ('U', 'Twenty-one'): The expression 'B' does not match 'U', so this pair is not considered.
  6. ('N/A'): This is the default pair, which is considered when no other pairs match the expression. Since the expression 'B' does not match any of the previous pairs, the function returns 'N/A'.

Therefore, the result of the given DECODE function is 'N/A', which corresponds to Option B.

Evaluate this SQL statement: SELECT ename, sal, 12*sal+100 FROM emp; The SAL column stores the monthly salary of the employee. Which change must be made to the above syntax to calculate the annual compensation as "monthly salary plus a monthly bonus of $100, multiplied by 12"? Evaluate this SQL statement: SELECT ename, sal, 12*sal+100 FROM emp; The SAL column stores the monthly salary of the employee. Which change must be made to the above syntax to calculate the annual compensation as "monthly salary plus a monthly bonus of $100, multiplied by 12"? A. No change is required to achieve the desired results. B. SELECT ename, sal, 12*(sal+100) FROM emp; C. SELECT ename, sal, (12*sal)+100 FROM emp; D. SELECT ename, sal+100,*12 FROM emp;

technology databases

  1. A

  2. B

  3. C

  4. D

Show answer
Correct Option: B
Explanation:

To calculate the annual compensation as monthly salary plus a monthly bonus of $100, multiplied by 12, we need to modify the expression "12*sal+100" in the SELECT statement.

Option A: No change is required to achieve the desired results. This option is incorrect because the original expression "12*sal+100" calculates the total compensation as monthly salary multiplied by 12, plus a fixed monthly bonus of $100. It does not add the bonus to the monthly salary before multiplying by 12.

Option B: SELECT ename, sal, 12*(sal+100) FROM emp; This option is correct. By adding the monthly bonus of $100 to the monthly salary before multiplying by 12, we get the correct annual compensation. The expression "12*(sal+100)" calculates the annual compensation as monthly salary plus bonus, multiplied by 12.

Option C: SELECT ename, sal, (12*sal)+100 FROM emp; This option is incorrect because the parentheses around "12*sal" are unnecessary. The multiplication operator has higher precedence than the addition operator, so "12*sal" is evaluated before adding 100.

Option D: SELECT ename, sal+100,12 FROM emp; This option is incorrect because the syntax is incorrect. The asterisk () is not a valid operator in this context. We need to use the multiplication operator (*) to calculate the annual compensation.

Therefore, the correct answer is: B. SELECT ename, sal, 12*(sal+100) FROM emp;

Which of the following is NOT a benefit of indexes?
technology databases

  1. Faster operation during INSERT commands

  2. Faster operation during UPDATE commands

  3. Faster operation during SELECT commands

  4. Faster operation during DELETE commands

Show answer
Correct Option: D

Which of the following commands will rename a table?
technology databases

  1. RENAME table_name new_table_name;

  2. RENAME table_name TO new_table_name;

  3. RENAME TABLE table_name new_table_name;

  4. RENAME TABLE table_name TO new_table_name;

Show answer
Correct Option: B
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