MS SQL Server - 27 - Correlated Subqueries MCQ

27 – Correlated Subqueries MCQ

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1. What is a correlated subquery in SQL Server?

A subquery that uses a different database

A subquery that references a column from the outer query

A subquery that returns multiple result sets

A subquery that returns aggregate values

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2. In SQL Server, what is the primary purpose of using a correlated subquery?

To enforce data integrity

To create a temporary table

To improve query performance

To eliminate duplicate rows

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3. Which SQL clause is commonly used to introduce correlated subqueries in SQL Server?

FROM

ORDER BY

WHERE

GROUP BY

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4. In a correlated subquery in SQL Server, which tables are typically involved?

The outer query table and the subquery table

Two subqueries

Two unrelated tables

The system tables

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5. What is the result of a correlated subquery if the subquery returns no rows in SQL Server?

A value of 0

NULL

An empty string

An error is thrown

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6. Which SQL function is commonly used in correlated subqueries to check for the existence of a row in a subquery result?

EXIST

COUNT

EXISTS

CHECK

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7. In SQL Server, what does the EXISTS function return if the subquery contains at least one row?

True

An error is thrown

NULL

False

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8. What is the primary difference between the EXISTS function and the IN operator in SQL Server?

The EXISTS function is used for correlated subqueries, while the IN operator is used for non-correlated subqueries.

The EXISTS function is used for mathematical operations, while the IN operator is used for string manipulation.

They are interchangeable, and either can be used in any subquery.

The IN operator is used for correlated subqueries, while the EXISTS function is used for non-correlated subqueries.

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9. In SQL Server, which keyword is commonly used with the EXISTS function in a subquery?

WHERE

EXISTS

VALIDATE

CHECK

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10. What is the result of a correlated subquery if the subquery returns multiple rows in SQL Server?

An error is thrown

The subquery result is used as-is

NULL

The subquery is automatically limited to a single row

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11. In SQL Server, which operator is used to combine the results of two or more queries and return only distinct rows?

EXCEPT

INTERSECT

UNION

UNION ALL

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12. When using the EXISTS function in a correlated subquery, what happens if the subquery is an empty result set?

The EXISTS function returns NULL.

The EXISTS function returns FALSE.

The EXISTS function returns TRUE.

An error is thrown.

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13. What is the primary purpose of the EXISTS function in a correlated subquery?

To concatenate values from the subquery

To count the number of rows in the subquery

To calculate the average of the subquery result

To check whether at least one row exists in the subquery

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14. In SQL Server, when is the EXISTS function typically used within a correlated subquery?

In the FROM clause

In the HAVING clause

In the SELECT clause

In the WHERE clause

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15. In a correlated subquery using the EXISTS function, what is the result if the subquery contains NULL values?

An error is thrown.

The EXISTS function returns TRUE.

The EXISTS function returns NULL.

The EXISTS function returns FALSE.

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16. Which SQL operator can be used to return rows that are not found in a correlated subquery result?

UNION ALL

UNION

INTERSECT

EXCEPT

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17. In SQL Server, what is the primary use of a correlated subquery with the EXISTS function?

To create a temporary table

To filter rows based on a condition

To join multiple tables

To return a single value

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18. When using the EXISTS function in a correlated subquery, which keyword is commonly used to specify the subquery’s alias?

ALIAS

SUBQUERY

SUB

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19. In a correlated subquery using the EXISTS function, which tables are involved?

The system tables

Two unrelated tables

The outer query table and the subquery table

Two subqueries

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20. In SQL Server, what does the EXISTS function return if the subquery contains rows with NULL values?

True

False

NULL

An error is thrown

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21. What is the result of a correlated subquery using the EXISTS function if the subquery is empty?

The EXISTS function returns FALSE.

The EXISTS function returns NULL.

An error is thrown.

The EXISTS function returns TRUE.

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22. In SQL Server, which SQL clause is typically used to filter rows in a correlated subquery with the EXISTS function?

WHERE

SELECT

GROUP BY

FROM

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MS SQL Server – 27 – Correlated Subqueries MCQ