DEA-C02 Data Transformation Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  OBJECT_KEYS(tags)

  Why it's wrong here

  OBJECT_KEYS returns the keys of a VARIANT object, not the elements of an array. Applying it to an array will not produce the tag values and is the wrong function for this scenario. It is used when working with JSON objects to list their attribute names.

• ✗

  ARRAY_TO_STRING(tags, ',')

  Why it's wrong here

  ARRAY_TO_STRING concatenates array elements into a single delimited string. It does not produce one row per element, so it cannot be used to expand the array into multiple rows for aggregation. This function is useful for display or export, but not for row-level transformation.

• ✓

  FLATTEN(input => tags)

  Why this is correct

  FLATTEN is a table function that expands a VARIANT array into one row per element, exposing the value in a VALUE column. It is the standard Snowflake construct for unnesting arrays and is exactly what is needed to transform the `tags` array into rows for downstream aggregation.

• ✗

  PARSE_JSON(tags)

  Why it's wrong here

  PARSE_JSON converts a string containing JSON into a VARIANT value. Since `tags` is already a VARIANT array, this function does not expand it into rows and may even fail or return the same array. It is used for parsing raw JSON strings, not for unnesting arrays.