Single-Row Functions can return multiple results per row.

Single-row functions return exactly ONE result per input row, not multiple results. This is why they're called 'single-row' functions - they maintain a one-to-one relationship between input rows and output rows. They may transform the data (change data type, format, etc.), but they never produce multiple output rows from a single input row. Multiple-row functions (aggregates) can reduce many rows to one result, but single-row functions do not.