Currently, external functions must be scalar functions.

• A. Columnar functions
• B. Table-valued functions
• C. Window functions
• D. Scalar functions

Answer: (D)

External functions in Snowflake are designed as a bridge to code running outside Snowflake, and each invocation returns a single value of a scalar type (such as a number, string, or boolean). This means you get one result per input row, not a set of rows. If you need multiple rows or a table-like result, that would require a different approach (for example, returning a single structured value like a JSON/VARIANT and expanding it in SQL, or using a different function type). Therefore, the current behavior is that external functions are scalar. Window functions and other multi-row concepts are about returning multiple results across a window or across rows, which isn’t how external functions operate.