Test Your Microsoft SQL Server DISTINCT Clause Knowledge with This Quiz

Progress

True / False

The query 'SELECT DISTINCT column_name FROM table_name' will remove duplicate values in 'column_name'.

True False

The DISTINCT keyword will ensure that all values in 'column_name' are unique in the result set, removing duplicates.

True / False

DISTINCT can be applied to multiple columns to ensure unique combinations of those columns.

True False

When DISTINCT is applied to multiple columns, it returns unique combinations of all specified columns, not just unique values in one column.

True / False

The query 'SELECT DISTINCT * FROM table_name' removes duplicates based on all columns in 'table_name'.

True False

Using DISTINCT with '*' ensures that all rows are unique across all columns. If two rows have the same values in all columns, one will be removed.

True / False

DISTINCT can be used with aggregate functions like COUNT() to count only unique values.

True False

DISTINCT can be used inside aggregate functions such as COUNT() to count unique values. For example, 'SELECT COUNT(DISTINCT column_name) FROM table_name' counts unique values in 'column_name'.

True / False

Applying DISTINCT with an ORDER BY clause can affect the performance of the query significantly.

True False

Using DISTINCT with ORDER BY can affect performance due to the additional sorting and duplication removal processes required.

True / False

The query 'SELECT DISTINCT column_name FROM table_name WHERE column_name = value' will return only distinct values of 'column_name' that match 'value'.

True False

The DISTINCT keyword works with the WHERE clause to filter and return only unique values in 'column_name' that meet the specified condition.

True / False

DISTINCT can be used with JOIN operations to remove duplicates from the joined result set.

True False

DISTINCT is useful in JOIN operations to remove duplicate rows resulting from combining multiple tables.

True / False

Using DISTINCT with subqueries will ensure the subquery results contain unique rows before applying the outer query.

True False

DISTINCT used in a subquery will ensure that the subquery result set contains only unique rows before the outer query processes it.

True / False

The DISTINCT keyword affects only the result set of a SELECT statement, not the actual data in the table.

True False

DISTINCT does not modify the data stored in the table; it only affects the result set returned by the SELECT statement.

Q10

True / False

DISTINCT can be used in a query with multiple columns to ensure each combination of those columns is unique.

True False

When DISTINCT is applied to multiple columns, it ensures that the result set contains unique combinations of the values across those columns.

Q11

True / False

The query 'SELECT DISTINCT column_name FROM table_name ORDER BY column_name' will return unique values of 'column_name' sorted in ascending order.

True False

The DISTINCT keyword removes duplicates, and the ORDER BY clause sorts the unique values in ascending order by default.

Q12

True / False

DISTINCT can be combined with GROUP BY to ensure that each group of data is unique.

True False

DISTINCT and GROUP BY are used for different purposes; DISTINCT removes duplicates, while GROUP BY aggregates data based on specified columns.

Q13

True / False

DISTINCT can handle NULL values by treating all NULLs as duplicates.

True False

DISTINCT treats all NULL values as equal, so if multiple rows have NULLs in the same column, only one NULL will appear in the result set.

Q14

True / False

Using DISTINCT with large datasets will always significantly slow down query performance.

True False

While DISTINCT can impact performance, the degree of impact depends on various factors including indexing, data volume, and query optimization.

Q15

True / False

The DISTINCT keyword will not work with subqueries that include aggregate functions like SUM or AVG.

True False

DISTINCT can be used in subqueries with aggregate functions to ensure the results are unique. For example, 'SELECT DISTINCT column_name FROM (SELECT SUM(column_name) FROM table_name) AS subquery'.

Q16

Single Choice

What is the result of the query 'SELECT DISTINCT column_name FROM table_name'?

All unique values from 'column_name' All rows from 'table_name' The first value of 'column_name'The count of distinct values

The query will return all unique values from 'column_name' in the 'table_name' table.

Q17

Single Choice

Which query will return unique combinations of 'column1' and 'column2'?

SELECT DISTINCT column1, column2 FROM table_name SELECT DISTINCT column1 FROM table_name SELECT DISTINCT column2 FROM table_nameSELECT column1, column2 FROM table_name

'SELECT DISTINCT column1, column2 FROM table_name' will return unique combinations of both columns.

Q18

Single Choice

How do you count the number of distinct values in 'column_name'?

SELECT COUNT(DISTINCT column_name) FROM table_name SELECT DISTINCT COUNT(column_name) FROM table_name SELECT COUNT(column_name) FROM table_nameSELECT DISTINCT(column_name) FROM table_name

The query 'SELECT COUNT(DISTINCT column_name) FROM table_name' will count the number of unique values in 'column_name'.

Q19

Single Choice

Which clause can be used with DISTINCT to sort the result set?

ORDER BY GROUP BY HAVINGWHERE

The ORDER BY clause can be used with DISTINCT to sort the result set.

Q20

Single Choice

What will the query 'SELECT DISTINCT column_name FROM table_name WHERE column_name IS NOT NULL' do?

Return unique values of 'column_name' that are not NULL Return all values of 'column_name' that are not NULL Return unique values of 'column_name' including NULLsReturn all rows where 'column_name' is NULL

This query will return unique values of 'column_name' that are not NULL.

Q21

Single Choice

How do you use DISTINCT with multiple columns?

SELECT DISTINCT column1, column2 FROM table_name SELECT DISTINCT column1 FROM table_name, column2 SELECT DISTINCT(column1, column2) FROM table_nameSELECT column1, DISTINCT column2 FROM table_name

To use DISTINCT with multiple columns, you include all desired columns in the SELECT statement, e.g., 'SELECT DISTINCT column1, column2 FROM table_name'.

Q22

Single Choice

In the query 'SELECT DISTINCT column1, column2 FROM table_name', which statement is true?

Returns unique combinations of values in 'column1' and 'column2' Returns unique values of 'column1' Returns unique values of 'column2'Returns all rows from 'table_name'

The query returns unique combinations of values in 'column1' and 'column2'.

Q23

Single Choice

What does the query 'SELECT DISTINCT COUNT(column_name) FROM table_name' return?

An error The count of unique values in 'column_name' The count of all values in 'column_name'All distinct values in 'column_name'

This query will result in an error as COUNT() cannot be used directly with DISTINCT in this manner. The correct usage is 'SELECT COUNT(DISTINCT column_name) FROM table_name'.

Q24

Single Choice

Which of the following queries correctly uses DISTINCT to find unique non-NULL values in 'column_name'?

SELECT DISTINCT column_name FROM table_name WHERE column_name IS NOT NULL SELECT DISTINCT(column_name IS NOT NULL) FROM table_name SELECT column_name FROM table_name WHERE DISTINCT column_name IS NOT NULLSELECT DISTINCT column_name IS NOT NULL FROM table_name

The correct query is 'SELECT DISTINCT column_name FROM table_name WHERE column_name IS NOT NULL'.

Q25

Single Choice

How do you select unique rows based on all columns from 'table_name'?

SELECT DISTINCT * FROM table_name SELECT DISTINCT column1, column2, ... FROM table_name SELECT DISTINCT ALL FROM table_nameSELECT * FROM table_name WHERE DISTINCT

To select unique rows based on all columns, use 'SELECT DISTINCT * FROM table_name'.

Q26

Single Choice

Fill in the blank: SELECT DISTINCT ____ FROM table_name.

column_name * COUNT(column_name)SUM(column_name)

The correct term to complete the statement is 'column_name'.

Q27

Single Choice

In which scenario is using DISTINCT most beneficial?

When removing duplicates from the result set When counting the total number of rows When performing a JOIN operationWhen using aggregate functions like SUM()

DISTINCT is most beneficial when you need to remove duplicates from the result set.

Q28

Single Choice

Which query correctly finds unique values from 'column_name' and orders them?

SELECT DISTINCT column_name FROM table_name ORDER BY column_name SELECT DISTINCT column_name ORDER BY column_name FROM table_name SELECT column_name DISTINCT FROM table_name ORDER BY column_nameSELECT DISTINCT column_name FROM table_name GROUP BY column_name

The correct query is 'SELECT DISTINCT column_name FROM table_name ORDER BY column_name'.

Q29

Single Choice

Fill in the blank: SELECT DISTINCT column_name FROM table_name WHERE ____.

column_name = value DISTINCT column_name column_name IS DISTINCTcolumn_name

The WHERE clause is used to filter rows based on a condition, e.g., 'column_name = value'.

Q30

Single Choice

Which query uses DISTINCT with multiple columns and orders the result?

SELECT DISTINCT column1, column2 FROM table_name ORDER BY column1, column2 SELECT column1, column2 DISTINCT FROM table_name ORDER BY column1, column2 SELECT DISTINCT column1, column2 ORDER BY column1, column2 FROM table_nameSELECT column1, column2 FROM table_name ORDER BY DISTINCT

The correct query is 'SELECT DISTINCT column1, column2 FROM table_name ORDER BY column1, column2'.

Q31

Multiple Choice

Which of the following are true about this query?

SQL Code

SELECT DISTINCT column1, column2
FROM table_name
WHERE column3 IN ('value1', 'value2')
ORDER BY column1 DESC;

It will return distinct combinations of column1 and column2 The rows will be filtered based on column3 values The result set will be ordered by column1 in descending orderThe DISTINCT keyword affects the ORDER BY clause

The DISTINCT keyword ensures unique combinations of column1 and column2, the WHERE clause filters rows based on column3, and the results are ordered by column1 in descending order.

Q32

Multiple Choice

In which scenarios can the DISTINCT keyword be used?

With single columns With multiple columns Inside aggregate functions like COUNT()To remove NULL values

DISTINCT can be used with single or multiple columns and inside aggregate functions like COUNT().

Q33

Multiple Choice

Which queries will return unique rows from 'table_name'?

SELECT DISTINCT * FROM table_name SELECT DISTINCT column1, column2 FROM table_name SELECT column1 DISTINCT FROM table_nameSELECT DISTINCT(column_name) FROM table_name

'SELECT DISTINCT * FROM table_name' and 'SELECT DISTINCT column1, column2 FROM table_name' will return unique rows.

Q34

Multiple Choice

Which of the following queries will correctly count unique values in 'column_name'?

SELECT COUNT(DISTINCT column_name) FROM table_name SELECT DISTINCT COUNT(column_name) FROM table_name SELECT COUNT(column_name) FROM table_name WHERE column_name IS DISTINCTSELECT COUNT(DISTINCT(column_name)) FROM table_name

'SELECT COUNT(DISTINCT column_name) FROM table_name' will count unique values correctly.

Q35

Multiple Choice

Which queries will sort unique values from 'column_name'?

Queries 'SELECT DISTINCT column_name FROM table_name ORDER BY column_name' and 'SELECT DISTINCT column_name ORDER BY column_name FROM table_name' will sort unique values.

Q36

Multiple Choice

Which queries can return unique non-NULL values?

SELECT DISTINCT column_name FROM table_name WHERE column_name IS NOT NULL SELECT DISTINCT(column_name) FROM table_name WHERE column_name IS NOT NULL SELECT DISTINCT column_name FROM table_nameSELECT DISTINCT(column_name IS NOT NULL) FROM table_name

Queries 'SELECT DISTINCT column_name FROM table_name WHERE column_name IS NOT NULL' and 'SELECT DISTINCT(column_name) FROM table_name WHERE column_name IS NOT NULL' can return unique non-NULL values.

Q37

Multiple Choice

Which queries use DISTINCT correctly in subqueries?

SELECT * FROM (SELECT DISTINCT column_name FROM table_name) AS subquery SELECT DISTINCT column_name FROM (SELECT column_name FROM table_name) AS subquery SELECT COUNT() FROM (SELECT DISTINCT column_name FROM table_name) AS subquerySELECT column_name DISTINCT FROM (SELECT column_name FROM table_name) AS subquery

Queries 'SELECT * FROM (SELECT DISTINCT column_name FROM table_name) AS subquery' and 'SELECT COUNT() FROM (SELECT DISTINCT column_name FROM table_name) AS subquery' use DISTINCT correctly in subqueries.

Q38

Multiple Choice

Which scenarios correctly apply the DISTINCT keyword?

Removing duplicates from a single column Removing duplicates from multiple columns Within subqueriesCombining with GROUP BY to aggregate data

DISTINCT is applied correctly in scenarios involving single columns, multiple columns, and within subqueries.

Q39

Multiple Choice

Which queries will return unique combinations of 'column1' and 'column2'?

SELECT DISTINCT column1, column2 FROM table_name SELECT DISTINCT(column1, column2) FROM table_name SELECT column1, column2 DISTINCT FROM table_nameSELECT DISTINCT column1, column2 ORDER BY column1, column2

Queries 'SELECT DISTINCT column1, column2 FROM table_name' and 'SELECT DISTINCT(column1, column2) FROM table_name' will return unique combinations.

Q40

Multiple Choice

Which queries will return unique rows from 'table_name' considering all columns?

SELECT DISTINCT * FROM table_name SELECT DISTINCT column1, column2, column3 FROM table_name SELECT DISTINCT(column1, column2, column3) FROM table_nameSELECT column1, column2, column3 DISTINCT FROM table_name

'SELECT DISTINCT * FROM table_name' will return unique rows considering all columns.

Q41

Multiple Choice

Which queries correctly use DISTINCT with aggregate functions?

SELECT COUNT(DISTINCT column_name) FROM table_name SELECT SUM(DISTINCT column_name) FROM table_name SELECT DISTINCT SUM(column_name) FROM table_nameSELECT AVG(DISTINCT column_name) FROM table_name

Queries 'SELECT COUNT(DISTINCT column_name) FROM table_name' and 'SELECT SUM(DISTINCT column_name) FROM table_name' correctly use DISTINCT with aggregate functions.

Q42

Multiple Choice

Which queries will return unique non-NULL values from 'column_name'?

Queries 'SELECT DISTINCT column_name FROM table_name WHERE column_name IS NOT NULL' and 'SELECT DISTINCT(column_name) FROM table_name WHERE column_name IS NOT NULL' will return unique non-NULL values.

Q43

Multiple Choice

Which queries can be used to select unique rows based on multiple columns?

Queries 'SELECT DISTINCT column1, column2 FROM table_name' and 'SELECT DISTINCT(column1, column2) FROM table_name' can be used to select unique rows based on multiple columns.

Q44

Multiple Choice

Which scenarios benefit from using the DISTINCT keyword?

Removing duplicates from the result set Finding unique values Combining with aggregate functionsUsing with JOIN operations

DISTINCT is beneficial when you need to remove duplicates, find unique values, or combine with aggregate functions.

Q45

Multiple Choice

Which queries use DISTINCT correctly to return unique values from 'column_name'?

SELECT DISTINCT column_name FROM table_name SELECT DISTINCT(column_name) FROM table_name SELECT DISTINCT column_name ORDER BY column_nameSELECT column_name DISTINCT FROM table_name

Queries 'SELECT DISTINCT column_name FROM table_name' and 'SELECT DISTINCT(column_name) FROM table_name' use DISTINCT correctly.

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