Tag: databases

Questions Related to databases

Evaluate these two SQL statements: SELECT last_name, salary , hire_date FROM EMPLOYEES ORDER BY salary DESC; SELECT last_name, salary, hire_date FROM EMPLOYEES ORDER BY 2 DESC; What is true about them?
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  1. The two statements produce identical results.

  2. The second statement returns a syntax error.

  3. There is no need to specify DESC because the results are sorted in descending order by default.

  4. The two statements can be made to produce identical results by adding a column alias for the salary column in the second SQL statement.

Show answer
Correct Option: A
Explanation:

To understand these SQL statements, the user needs to know how to query a database and sort the results in descending order based on a specific column.

The first SQL statement selects the last name, salary, and hire date columns from the EMPLOYEES table and orders the results by salary in descending order using the ORDER BY clause with the DESC keyword.

The second SQL statement is identical to the first one but uses the shorthand ORDER BY 2 DESC instead of explicitly specifying the salary column name.

Now let's go through each option and explain why it is right or wrong:

A. The two statements produce identical results: This option is correct. Both SQL statements select the same columns and sort the results in the same descending order based on the salary column. The shorthand ORDER BY 2 DESC in the second statement refers to the second column in the SELECT clause, which is the salary column.

B. The second statement returns a syntax error: This option is incorrect. The second SQL statement is a valid syntax and produces the same results as the first one.

C. There is no need to specify DESC because the results are sorted in descending order by default: This option is incorrect. SQL sorts the results in ascending order by default, so the DESC keyword is needed to sort the results in descending order.

D. The two statements can be made to produce identical results by adding a column alias for the salary column in the second SQL statement: This option is incorrect. Adding a column alias does not change the way the ORDER BY clause works. It only renames the column in the result set.

The Answer is: A

Which four statements correctly describe functions that are available in SQL? (Choose four.)

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  1. INSTR returns the numeric position of a named character.

  2. NVL2 returns the first non-null expression in the expression list.

  3. TRUNCATE rounds the column, expression, or value to n decimal places.

  4. DECODE translates an expression after comparing it to each search value.

  5. TRIM trims the heading or trailing characters (or both) from a character string.

  6. NULLIF compares two expressions and returns null if they are equal, or the first expression if they are not equal.

Show answer
Correct Option: A,D,E,F

AI Explanation

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

Option A) INSTR returns the numeric position of a named character. - This option is correct. The INSTR function in SQL returns the position of a specified character or substring within a string.

Option B) NVL2 returns the first non-null expression in the expression list. - This option is incorrect. The NVL2 function in SQL returns the second expression if the first expression is not null, otherwise, it returns the third expression.

Option C) TRUNCATE rounds the column, expression, or value to n decimal places. - This option is incorrect. The TRUNCATE function in SQL is used to remove all rows from a table or a partition, not to round values.

Option D) DECODE translates an expression after comparing it to each search value. - This option is correct. The DECODE function in SQL compares an expression to each search value and returns a result based on the match.

Option E) TRIM trims the heading or trailing characters (or both) from a character string. - This option is correct. The TRIM function in SQL removes leading and trailing characters (or both) from a character string.

Option F) NULLIF compares two expressions and returns null if they are equal, or the first expression if they are not equal. - This option is correct. The NULLIF function in SQL compares two expressions and returns null if they are equal, or the first expression if they are not equal.

The four correct statements are A) INSTR, D) DECODE, E) TRIM, and F) NULLIF.

Which statement creates a new user?
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  1. CREATE USER Susan;

  2. CREATE OR REPLACE USER Susan;

  3. CREATE NEW USER Susan DEFAULT;

  4. CREATE USER Susan IDENTIFIED BY blue;

  5. CREATE NEW USER Susan IDENTIFIED by blue;

  6. CREATE OR REPLACE USER Susan IDENTIFIED BY blue;

Show answer
Correct Option: D

Mark for review Which SQL statement accepts user input for the columns to be displayed, the table name, and the WHERE condition?
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  1. SELECT &1, "&2"FROM &3 WHERE last_name = '&4';

  2. SELECT &1, '&2' FROM &3 WHERE '&last_name = '&4'';

  3. SELECT &1, &2 FROM &3 WHERE last_name = '&4';

  4. SELECT &1, '&2' FROM EMP WHERE last_name = '&4';

Show answer
Correct Option: C

The user Sue issues this SQL statement: GRANT SELECT ON sue.EMP TO Alice WITH GRANT OPTION; The user Alice issues this SQL statement: GRANT SELECT ON sue.EMP TO Rena WITH GRANT OPTION; The user Rena issues this SQL statement: GRANT SELECT ON sue.EMP TO timber; The user Sue issues this SQL statement: REVOKE select on sue.EMP FROM Alice; For which users does the revoke command revoke SELECT privileges on the SUE.EMP table?

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  1. Alice only

  2. Alice and Rena

  3. Alice, Rena, and Timber

  4. Sue, Alice, Rena, and Timber

Show answer
Correct Option: C

AI Explanation

To determine which users have their SELECT privileges revoked on the SUE.EMP table, we need to analyze the SQL statements provided.

Initially, Sue grants SELECT privileges on sue.EMP to Alice with the GRANT OPTION. This means that Alice can grant these privileges to other users.

Then, Alice grants SELECT privileges on sue.EMP to Rena with the GRANT OPTION. Rena can also grant these privileges to other users.

Finally, Rena grants SELECT privileges on sue.EMP to Timber without the GRANT OPTION.

Afterward, Sue revokes the SELECT privileges on sue.EMP from Alice.

When a user grants privileges with the GRANT OPTION, they can pass on those privileges to other users. However, when a user grants privileges without the GRANT OPTION, they cannot pass on those privileges.

Therefore, the REVOKE command issued by Sue will revoke the SELECT privileges on sue.EMP from Alice. Since Alice granted these privileges to Rena with the GRANT OPTION, Rena will still have the SELECT privileges on sue.EMP. However, since Rena granted these privileges to Timber without the GRANT OPTION, Timber will also lose the SELECT privileges on sue.EMP.

Hence, the correct answer is:

C. Alice, Rena, and Timber

IDMS stands for _____________?

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  1. Integrated Data Management System

  2. Integrated Database Management System

  3. Integrated Database Messaging System

  4. Internal Database Management System

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Correct Option: B

IDMS is ______ type of database.
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  1. Hierarchical

  2. Relational

  3. Network

  4. Other

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Correct Option: C

In IDMS terminology, a parent record is called an ________ and a child record is called a ______.
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  1. Owner and Child

  2. Head and Child

  3. Owner and Member

  4. Head and Tail

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Correct Option: C

The unit of data that is passed by IDMS from database to application program is known as ________.

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  1. Set

  2. Page

  3. Area

  4. Record Type

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Correct Option: D

The relationship between 2 or more record types is defined by ___?

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  1. Area

  2. Set Type

  3. Record Type

  4. Relation

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Correct Option: B