Which are aggregate functions?
Interviewer Expectations for this Question
01
Core Competency
Assesses fundamental understanding of SQL & Databases conventions, runtime behavior, and memory/performance considerations.
02
Evaluation Criteria
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
Comprehensive Model Answer
Verified Solution
Aggregate functions perform a computation on a set of values across multiple rows and return a single summarizing value:
### Core Standard Aggregate Functions:
COUNT(): Returns the number of rows or non-null values.SUM(): Computes the mathematical sum of numeric values.AVG(): Computes the arithmetic mean of numeric values (automatically ignores NULLs).MIN(): Returns the minimum value (numeric, string, or date).MAX(): Returns the maximum value.
### Statistical & String Aggregates:
GROUP_CONCAT()(MySQL) /STRING_AGG()(PostgreSQL/SQL Server): Concatenates strings from a group.STDDEV(),VARIANCE(): Statistical dispersion calculations.
Candidate Response Strategy & Interview Tips
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- Discuss complexity & edge cases: Proactively explain time/space complexity or boundary conditions (null values, scale limits).
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