MCQs

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Overall MCQs for Reference

Which aggregate function returns the total sum of values in a column?
a. MIN()
b. AVG()
c. SUM()
d. COUNT()
Answer: c. SUM()testbook+2
Which function is used to count the number of rows, including duplicates?
a. AVG()
b. SUM()
c. COUNT()
d. MIN()
Answer: c. COUNT()sciencedirect+2
What does the AVG() function calculate?
a. Total count
b. Mean value
c. Maximum value
d. Minimum value
Answer: b. Mean valuegeeksforgeeks+2
Which aggregate function returns the lowest value in a column?
a. MIN()
b. MAX()
c. SUM()
d. COUNT()
Answer: a. MIN()stratascratch+2
In which scenario does COUNT(DISTINCT column) differ from COUNT(column)?
a. When values are unique
b. When duplicates exist
c. Only on numeric data
d. Never
Answer: b. When duplicates existsciencedirect+1
Which function finds the highest value in a group of data?
a. MIN()
b. SUM()
c. AVG()
d. MAX()
Answer: d. MAX()testbook+2
What does the SUM() function ignore while computing totals?
a. Negative values
b. NULL values
c. String values
d. Zeroes
Answer: b. NULL valuesw3schools+2
Which aggregate function can be used with both numbers and strings for comparison?
a. AVG()
b. MIN()
c. SUM()
d. None
Answer: b. MIN()stratascratch
Which aggregate function does not eliminate NULL values?
a. COUNT()
b. SUM()
c. AVG()
d. MAX()
Answer: a. COUNT()geeksforgeeks+1
Which is not an aggregate function in standard SQL?
a. AVG()
b. MAX()
c. TOTAL()
d. COUNT()
Answer: c. TOTAL()sanfoundry
What is the result of COUNT(column) when the column contains NULLs?
a. All rows counted
b. Only non-NULL rows counted
c. NULL returned
d. Error
Answer: b. Only non-NULL rows countedsciencedirect+1
Which function returns the average of values in a column, ignoring NULLs?
a. MIN()
b. SUM()
c. AVG()
d. MAX()
Answer: c. AVG()simplilearn+2
What is the property of a distributive aggregate function?
a. Can be split across partitions
b. Requires all data in memory
c. Always returns count
d. Computes rank
Answer: a. Can be split across partitionssciencedirect
Which aggregate function can detect outliers in a dataset?
a. COUNT()
b. AVG()
c. SUM()
d. DISTINCT()
Answer: b. AVG()simplilearn
What clause is commonly paired with aggregate functions to group results?
a. ORDER BY
b. GROUP BY
c. WHERE
d. HAVING
Answer: b. GROUP BYw3schools+1
Which function would you use to find the number of unique employees?
a. COUNT(employee_id)
b. COUNT(DISTINCT employee_id)
c. SUM(employee_id)
d. AVG(employee_id)
Answer: b. COUNT(DISTINCT employee_id)sciencedirect
What does the HAVING clause do when used with aggregate functions?
a. Renames columns
b. Filters aggregate results
c. Sorts rows
d. Groups data
Answer: b. Filters aggregate resultsgeeksforgeeks+1
Which aggregate function can be defined as holistic?
a. MIN()
b. AVG()
c. SUM()
d. MEDIAN()
Answer: d. MEDIAN()sciencedirect
What is the output of SUM() in a column of only NULLs?
a. 0
b. NULL
c. Error
d. All values
Answer: b. NULLsimplilearn+1
Which aggregate function finds the most frequent value in a column?
a. MAX()
b. MODE()
c. COUNT()
d. SUM()
Answer: b. MODE()studocu
What does the DISTINCT keyword do with aggregate functions?
a. Includes unique values only
b. Excludes NULL values
c. Orders results
d. Joins tables
Answer: a. Includes unique values onlygeeksforgeeks+1
Which aggregate function would compute the variance of a dataset?
a. VAR()
b. AVG()
c. MIN()
d. MAX()
Answer: a. VAR()studocu
Which function helps summarize all incomes from a dataset?
a. COUNT()
b. MIN()
c. SUM()
d. AVG()
Answer: c. SUM()projectpro
Which aggregate function returns the first value when sorted ascending?
a. MAX()
b. MIN()
c. AVG()
d. COUNT()
Answer: b. MIN()stratascratch
What is the function of CHECKSUM_AGG in SQL?
a. Sums numeric values
b. Returns hash of dataset
c. Finds distinct values
d. Calculates average
Answer: b. Returns hash of datasetsimplilearn
Which aggregate function can operate on both numeric and non-numeric columns?
a. AVG()
b. MIN()
c. SUM()
d. CHECKSUM()
Answer: b. MIN()stratascratch
The COUNT(*) function returns:
a. Only unique rows
b. All rows, including NULLs
c. Only non-NULL rows
d. Rows with duplicates removed
Answer: b. All rows, including NULLsw3schools+1
Which aggregate function is an example of an algebraic function?
a. AVG()
b. COUNT()
c. SUM()
d. MIN()
Answer: a. AVG()sciencedirect
What would SUM(income) return if income is numeric but includes NULLs?
a. Total income including NULLs as zero
b. Excludes NULLs
c. Returns just NULL
d. Returns the maximum income
Answer: b. Excludes NULLsstratascratch+1
Which SQL clause allows aggregate functions to work on partitions of data?
a. GROUP BY
b. PARTITION BY
c. HAVING
d. ORDER BY
Answer: b. PARTITION BYsimplilearn
What is the major difference between COUNT() and COUNT(column)?
a. COUNT() includes NULLs, COUNT(column) excludes NULLs
b. Both include NULLs
c. COUNT() only works with numeric columns
d. COUNT(column) shows row numbers
Answer: a. COUNT() includes NULLs, COUNT(column) excludes NULLssciencedirect
Which aggregate function would help find the highest salary in a department?
a. MIN(salary)
b. MAX(salary)
c. AVG(salary)
d. SUM(salary)
Answer: b. MAX(salary)testbook+1
Which data summarization method does aggregation not cover by default?
a. Sum
b. Mean
c. Median
d. Count
Answer: c. Medianstudocu
Aggregate functions output:
a. Multiple values per group
b. One value per group
c. Row numbers
d. Data types
Answer: b. One value per groupinvestopedia+2
The aggregate function STD returns:
a. The sum of deviations
b. Standard deviation
c. Mean value
d. Median
Answer: b. Standard deviationstudocu
Which aggregate function performs calculation on a set and yields a single summary value?
a. Partition
b. Aggregate
c. Join
d. Union
Answer: b. Aggregateinvestopedia+1
What is required for aggregate functions to summarize datasets?
a. Table aliases
b. Grouping
c. Sorting
d. Limiting
Answer: b. Groupingw3schools+1
Which keyword removes duplicate entries before aggregation?
a. UNIQUE
b. DISTINCT
c. PRIMARY
d. SELECT
Answer: b. DISTINCTgeeksforgeeks+1
Which aggregate function can include conditionals, such as product type filtering?
a. SUM()
b. COUNT(*)
c. MIN()
d. AVG()
Answer: a. SUM()projectpro+1
For ranking values, which aggregate function is needed?
a. MAX()
b. MODE()
c. RANK()
d. AVG()
Answer: c. RANK()sciencedirect
Aggregate functions are useful for:
a. Summarizing data
b. Splitting tables
c. Formatting outputs
d. Encrypting data
Answer: a. Summarizing datainvestopedia+2
Which aggregate function computes the sum of all unique values?
a. SUM(DISTINCT column)
b. AVG(column)
c. MAX(column)
d. MIN(column)
Answer: a. SUM(DISTINCT column)sciencedirect
When grouping by department_id, what does SELECT AVG(salary) return?
a. Each employee’s salary
b. Average salary per department
c. Total salary
d. Count of departments
Answer: b. Average salary per departmenttestbook
Which aggregate function can be used to find the number of NULLs in a column?
a. COUNT(column)
b. AVG(column)
c. SUM(column)
d. COUNT() – COUNT(column)
Answer: d. COUNT() – COUNT(column)geeksforgeeks+1
What is indicated by an aggregate function returning a NULL?
a. Error in query
b. No values found
c. At least one value was NULL
d. Query is invalid
Answer: b. No values foundsimplilearn+1
Which aggregate function facilitates data integrity checking?
a. AVG()
b. CHECKSUM_AGG()
c. MAX()
d. COUNT()
Answer: b. CHECKSUM_AGG()simplilearn
What is the importance of SUM for financial datasets?
a. Finds averages
b. Totals transactions
c. Counts rows
d. Excludes duplicates
Answer: b. Totals transactionsprojectpro+1
Which function calculates the total number of non-NULL values in a column?
a. COUNT(column)
b. COUNT(*)
c. SUM(column)
d. MIN(column)
Answer: a. COUNT(column)geeksforgeeks+1
What happens if you apply AVG to a column with only NULLs?
a. AVG returns 0
b. AVG returns NULL
c. AVG returns maximum value
d. AVG returns first value
Answer: b. AVG returns NULLgeeksforgeeks+1
Which aggregate function would you use to get summary statistics from a table?
a. COUNT(), MIN(), MAX(), AVG(), SUM()
b. JOIN(), UNION()
c. SELECT(), INSERT()
d. DELETE(), DROP()
Answer: a. COUNT(), MIN(), MAX(), AVG(), SUM()projectpro+2

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