Tag: databases

Questions Related to databases

Which task can you perform using only the TO_CHAR function?
technology databases

  1. convert 10 to 'TEN'

  2. convert '10' to 10

  3. convert '10' to '10'

  4. convert 'TEN' to 10

Show answer
Correct Option: C

In which scenario would an index be most useful?
technology databases

  1. The indexed column is declared as NOT NULL.

  2. The indexed columns are used in the FROM clause.

  3. The indexed columns are part of an expression.

  4. The indexed column contains a wide range of values.

Show answer
Correct Option: D

Which operator can be used with a multiple-row subquery?

technology databases

  1. =

  2. LIKE

  3. BETWEEN

  4. NOT IN

  5. Is

  6. <>

Show answer
Correct Option: D

AI Explanation

To answer this question, you need to understand the concept of subqueries in SQL.

A subquery is a query that is nested inside another query. It is used to retrieve data from one or more tables and use that result in the outer query. In the case of a multiple-row subquery, the subquery returns more than one row.

When using a multiple-row subquery, you can use various operators to compare the result of the subquery with the outer query. The correct answer in this case is option D) NOT IN.

The NOT IN operator is used to exclude rows from the result set that match the values returned by the subquery. It returns rows from the outer query where the value of a specified column does not match any value returned by the subquery.

Here's an explanation of each option:

A. = (Equals) - This operator is used to compare two values for equality. However, it is not specifically designed to work with multiple-row subqueries.

B. LIKE - The LIKE operator is used to compare a value to a pattern. It is typically used for pattern matching with wildcard characters. It is not specifically designed to work with multiple-row subqueries.

C. BETWEEN - The BETWEEN operator is used to check if a value is within a range of values. It is not specifically designed to work with multiple-row subqueries.

D. NOT IN - This operator is used to exclude rows that match the values returned by the subquery. It is specifically designed to work with multiple-row subqueries.

E. IS - The IS operator is used to compare a value to NULL. It is not specifically designed to work with multiple-row subqueries.

F. <> (Not Equal) - This operator is used to compare two values for inequality. It is not specifically designed to work with multiple-row subqueries.

In conclusion, the correct answer is D) NOT IN because it is the operator specifically designed to work with multiple-row subqueries.

Which three SELECT statements display 2000 in the format "$2,000.00"? (Choose three.)
technology databases

  1. SELECT TO_CHAR(2000, '$#,###.##') from dual

  2. SELECT TO_CHAR(2000, '$0,000.00') from dual

  3. SELECT TO_CHAR(2000, '$9,999.00') from dual

  4. SELECT TO_CHAR(2000, '$9,999.99') from dual

  5. SELECT TO_CHAR(2000, '$2,000.00') FROM dual;

  6. SELECT TO_CHAR(2000, '$N,NNN.NN') FROM dual;

Show answer
Correct Option: B,C,D

Which of the following correctly describe the aggregate functions?
technology databases

  1. It returns a single result row based on single rows

  2. It returns a single result row based on groups of rows

  3. It can only appear in ORDER BY clauses

  4. It cannot appear in select lists

Show answer
Correct Option: B

Which of the following SQL statements can calculate and return the absolute value of -33?
technology databases

  1. SELECT ABS(-33) "Absolute" FROM DUAL;

  2. SELECT ABS(-33), Absolute FROM DUAL;

  3. SELECT ABS("-33") Absolute FROM DUAL;

  4. None of these

Show answer
Correct Option: A
Explanation:

To solve this question, the user needs to know the syntax for calculating the absolute value in SQL. The ABS function can be used to calculate the absolute value of a number.

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

A. SELECT ABS(-33) "Absolute" FROM DUAL; This option is correct. The ABS function is used to calculate the absolute value of a number, and the syntax in this statement is correct. The "Absolute" alias is used to rename the column with the calculated value.

B. SELECT ABS(-33), Absolute FROM DUAL; This option is incorrect. The "Absolute" alias is not defined in the statement. Additionally, the ABS function is used correctly.

C. SELECT ABS("-33") Absolute FROM DUAL; This option is incorrect. The quotation marks around the number indicate that it is a string, not a number. The ABS function cannot calculate the absolute value of a string.

D. None of these This option is incorrect. Option A is the correct answer.

The Answer is: A

What does the following SQL script do? SELECT AVG(MAX(salary)) FROM employees GROUP BY department_id;
technology databases

  1. it has a syntax error, the AVG clause is not valid

  2. it calculates the average of the maximum salaries of all the departments

  3. it has a syntax error, the MAX clause is not valid

  4. it has no error, but the GROUP BY clause is not effective

Show answer
Correct Option: B

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: A,B,C,D

AI Explanation

To answer this question, you need to understand the concept of Data Manipulation Language (DML). DML statements are used to manipulate the data stored in the database. Let's go through each option to understand why it is correct or incorrect:

Option A) COMMIT - This option is a DML statement. It is used to save the changes made to the database since the last COMMIT or ROLLBACK statement.

Option B) MERGE - This option is a DML statement. It is used to perform insert, update, or delete operations on a target table based on the results of a join with a source table.

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

Option D) DELETE - This option is a DML statement. It is used to delete existing records from a table.

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

Option F) DROP - This option is not a DML statement. DROP statements are part of the DDL and are used to remove database objects such as tables, indexes, and views.

The correct answers are A, B, C, and D. These options are correct because they are DML statements used for manipulating data in the database.

Which Function can return a non-Null value if passed null arguments?
technology databases

  1. NULLIF

  2. LENGTH

  3. CONCAT

  4. INSTR

  5. TAN

Show answer
Correct Option: C

SQL has facility for programmed handling of errors that arise during the manipulation of data.

technology databases

  1. True

  2. False

Show answer
Correct Option: B

AI Explanation

To answer this question, we need to understand the concept of error handling in SQL.

Option A) True - This option is incorrect. SQL does have facilities for error handling, such as the use of try-catch blocks or error handling functions like @@ERROR or TRY...CATCH. These features allow programmers to handle errors that may occur during data manipulation operations.

Option B) False - This option is correct. The statement is false because SQL does have facilities for handling errors during data manipulation.

The correct answer is B) False.