Single Row Function / Multiple Row Function

Single Row Functions

Operate on one row at a time and return one result per row, regardless of how many rows the query processes — for example, UPPER(name) or ROUND(salary, 2).

Multiple Row (Aggregate) Functions

Operate across a group of rows and return a single summarized result — for example, COUNT(*), SUM(salary), AVG(salary), MAX(salary), and MIN(salary).

Using GROUP BY

Aggregate functions are often combined with GROUP BY to summarize data per category, e.g. SELECT department, COUNT(*) FROM employees GROUP BY department;

Why the Distinction Matters for Testing

Knowing which type of function to use lets testers quickly verify things like total record counts, sums, or per-row transformations when validating data against expected results.