COF-C03 Practice Question: Performance Optimization, Querying, and Transformation

Answer analysis

Option-by-option breakdown

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

• ✗

  Use the TO_VARCHAR function to cast the entire VARIANT to a string and then use a JSON parser.

  Why it's wrong here

  Casting the entire VARIANT to a string and then parsing it again is unnecessary and can lead to performance degradation. It also requires an external or additional JSON parser, which Snowflake does not require. The native colon operator or GET_PATH function directly accesses the value within the VARIANT, preserving type and avoiding extra processing. This approach is simpler and more efficient.

• ✓

  Use the colon operator (:) to access the value by key, for example variant_column:key_name.

  Why this is correct

  The colon operator allows direct access to a value within a VARIANT column using a key or path. For a JSON object, `variant_column:key_name` returns the value associated with that key. This is the simplest and most efficient way to extract a scalar value for use in a relational query. It is a core feature of Snowflake's semi-structured data support and does not require additional functions or table functions.

• ✗

  Use the FLATTEN function to explode the JSON object into rows.

  Why it's wrong here

  FLATTEN is used to explode arrays or objects into multiple rows, which is useful for normalizing nested data. However, for extracting a single scalar value from a JSON object, FLATTEN is not necessary and would produce multiple rows if the object contains arrays. The engineer needs a direct way to access a scalar, such as a path expression or the GET_PATH function, not a row-generating function.

• ✗

  Use the PARSE_JSON function to convert the VARIANT to a string and then use string functions.

  Why it's wrong here

  PARSE_JSON is used to parse a string into a VARIANT, not to extract values from an existing VARIANT. Converting a VARIANT to a string and then using string functions is inefficient and error-prone. It would require additional parsing and could lose type information. The colon operator or GET_PATH is the correct approach for extracting a scalar value from a VARIANT column.