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databases Online Quiz - 111

Description: databases Online Quiz - 111
Number of Questions: 20
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Tags: databases
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What is true of using group functions on columns that contain NULL Values

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  1. Group functions on columns ignore NULL values.

  2. Group functions on columns returning dates include NULL values

  3. Group functions on columns returning numbers include NULL values.

  4. Group functions on columns cannot be accurately used on columns that contain NULL values.

Show answer
Correct Option: A
Explanation:

To answer this question, the user needs to understand the behavior of group functions when used on columns that contain NULL values.

Option A is correct. Group functions ignore NULL values in columns. For example, the AVG function calculates the average of all non-NULL values, while the COUNT function counts all non-NULL values. This means that NULL values are not included in the calculation and do not affect the result.

Option B and Option C are incorrect because they describe the behavior of specific group functions, rather than the behavior of group functions in general. The behavior of each group function depends on the specific function being used and the data type of the column being aggregated.

Option D is incorrect because group functions can be accurately used on columns that contain NULL values. However, it is important to keep in mind that NULL values may affect the result of certain operations, such as the SUM function. If a column contains both NULL and non-NULL values, the SUM function will return a NULL value, unless the column is aggregated using the NVL function or a similar function that replaces NULL values with a default value.

Therefore, the correct answer is:

The Answer is: A. Group functions on columns ignore NULL values.

You cannot modify data in a view if it contains: Group functions such as SUM, MIN, MAX, AVG, … A GROUP BY clause. The DISTINCT keyword. Columns defined by expressions (i.e, SAL * 12). The ROWNUM pseudo column.

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  1. True

  2. False

Show answer
Correct Option: B

Which table should you query to determine when your procedure was last compiled?

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  1. USER_OBJECTS

  2. USER_PROCEDURES

  3. USER_PROCS

  4. USER_PLSQL_UNITS

Show answer
Correct Option: A

A transaction is a set of SQL statements between any two COMMIT and ROLLBACK statements

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  1. True

  2. False

Show answer
Correct Option: B

Which of the following syntax is correct for creating a proc

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  1. CREATE OR REPLACE PROCEDURE <> as

  2. CREATE OR REPLACE PROCEDURE <>(Parameter list) as

  3. CREATE OR REPLACE PROCEDURE <> is

  4. All of the above

Show answer
Correct Option: D

Choose correct statement below

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  1. When a parameter is passed as an IN variable it is passed by reference

  2. When variables are passed in OUT or INOUT mode it is pass by value

  3. The NOCOPY clause tells to PL/SQL engine to pass the variable by reference

  4. All of the above

Show answer
Correct Option: D

How can you migrate from a LONG to a LOB data type for a column?

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  1. Use the DBMS_MANAGE_LOB.MIGRATE procedure

  2. Use the UTL_MANAGE_LOB.MIGRATE procedure.

  3. Use the ALTER TABLE command

  4. You cannot migrate from a LONG to a LOB date type for a column

Show answer
Correct Option: C

You need to create a trigger on the EMP table that monitors every row that is changed and places this information into the AUDIT_TABLE. What type of trigger do you create?

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  1. FOR EACH ROW trigger on the EMP table.

  2. Statement-level trigger on the EMP table.

  3. FOR EACH ROW trigger on the AUDIT_TABLE table.

  4. Statement-level trigger on the AUDIT_TABLE table.

Show answer
Correct Option: A

NOARCHIVELOG mode does have the advantage of not having to write transactions to an archive log and thus increases the performance of the database slightly.

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  1. True

  2. False

Show answer
Correct Option: B

The ANALYZE command is used to gather statistics on a table

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  1. True

  2. False

Show answer
Correct Option: B

Before making a tablespace read only, which of the following conditions must be met

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  1. The tablespace must be online

  2. The tablespace must not contain any active rollback segments

  3. he tablespace must not be involved in an open backup

  4. All of the above

Show answer
Correct Option: D

Select correct type of parameter mode used in oracle

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  1. IN

  2. OUT

  3. IN OUT

  4. All of the above

Show answer
Correct Option: D

You need to remove the database trigger T1. Which command do you use to remove the trigger in the SQL *Plus environment?

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  1. DROP TRIGGER T1

  2. DELETE TRIGGER T1

  3. ALTER TRIGGER T1 DISABLE

  4. None of the above

Show answer
Correct Option: A

A cold backup is taking a backup of the database while it is shut down and does not require being in archive log mode.

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  1. True

  2. False

Show answer
Correct Option: B

What tablespace is automatically created when we create a database

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  1. The Default tablespace

  2. The temp tablespace

  3. The SYSTEM tablespace

  4. None of the above

Show answer
Correct Option: C

In which four clauses can a subquery be used?

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  1. in the INTO clause of an INSERT statement

  2. in the GROUP BY clause of a SELECT statement

  3. in the VALUES clause of an INSERT statement

  4. in the ORDER BY clause of a SELECT statement

Show answer
Correct Option: A

Uses of SSIS

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  1. to move data from one data source to another

  2. powerful ETL tool

  3. To design various kind of reports

  4. to provide business information to a wider audience within an organization

Show answer
Correct Option: A,B,D

What does the following SQL statement do: SELECT Customer, COUNT(Order) FROM Sales GROUP BY Customer HAVING COUNT(Order) >5

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  1. Selects the total number of orders from the Sales table, if this number is greater than 5

  2. Selects all customers from table Sales that have made more than 5 orders.

  3. Selects all Customers from the Sales table

  4. None of the above

Show answer
Correct Option: B
Explanation:

To understand this SQL statement, the user needs to know the basic structure of SQL queries. In this case, the statement selects two fields, Customer and COUNT(Order), from the Sales table. It then groups these fields by Customer and applies a filter using the HAVING clause to only return rows where the count of orders for that customer is greater than 5.

A. This option is incorrect because the statement is not selecting the total number of orders, but rather the count of orders for each customer.

B. This option is correct. The statement is selecting all customers from the Sales table that have made more than 5 orders.

C. This option is incorrect because the statement is not selecting all customers, but rather only those who have made more than 5 orders.

D. This option is incorrect because option B is correct.

Therefore, the answer is: B. Selects all customers from table Sales that have made more than 5 orders.

Which of the following SQL statements is correct?

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  1. TRUNCATE Sales TABLE

  2. TRUNCATE * FROM TABLE Sales

  3. TRUNCATE TABLE Sales

  4. All the above

Show answer
Correct Option: C

What is a stored procedure?

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  1. A process for data export/import.

  2. A set of SQL statements stored and executed as a single entity.

  3. A process to convert tables.

  4. Data stored in a database.

Show answer
Correct Option: B
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