Task 3.2: Develop a model and query semi-structured data using the VARIANT data type and related functions (e.g., parse_json, variant_get).

• Atry_variant_get(payload, '$.price', 'decimal(10,2)')

  Correct

  try_variant_get returns NULL when the path is missing or the value cannot be cast to the requested type.

• Bvariant_get(payload, '$.price', 'decimal(10,2)')

  Incorrect

  variant_get raises an error when the cast fails, which is the current failure.

• Cpayload:price::decimal(10,2)

  Incorrect

  The :: cast also raises an error for a value that cannot be cast.

• Dtry_parse_json(payload:price) to reparse the extracted field

  Incorrect

  Reparsing the extracted value does not cast it to DECIMAL, so price would still not be a number.

variant_get and the :: operator raise errors when a value cannot be cast. try_variant_get takes the same path and type arguments and returns NULL instead.

• Aschema_of_variant_agg(payload) over the table

  Correct

  This aggregate merges the schemas of all VARIANT values by field name and returns one DDL schema.

• Bschema_of_variant(payload) on the first row

  Incorrect

  This returns the schema of a single value, so fields missing from that row are left out.

• Cschema_of_json(to_json(payload)) on the first row

  Incorrect

  This also infers from one value and misses fields of other rows.

• DDESCRIBE TABLE on the table

  Incorrect

  DESCRIBE shows the column type VARIANT, not the structure inside it.

schema_of_variant_agg returns the combined schema of all VARIANT values in a group, merging fields by name and using the least common type when types differ. schema_of_variant works on a single value.

• Ais_variant_null(v:discount)

  Correct

  is_variant_null tests for a VARIANT-encoded null, which IS NULL does not treat as SQL NULL.

• Bv:discount = 'null'

  Incorrect

  That compares with the string 'null', not a JSON null value.

• Cisnull(v:discount)

  Incorrect

  isnull checks for SQL NULL, like IS NULL.

• Dv:discount <=> NULL

  Incorrect

  Null-safe equality with NULL is true only for a SQL NULL, and a VARIANT-encoded null is not a SQL NULL.

A JSON null inside a VARIANT is a VARIANT-encoded null, not a SQL NULL. is_variant_null returns true for it, while IS NULL checks whether the expression itself is SQL NULL.

• Aparse_json(raw)

  Incorrect

  parse_json raises an error on malformed JSON.

• Bschema_of_json(raw)

  Incorrect

  schema_of_json returns the schema of a JSON string in DDL format, not a VARIANT value.

• Ctry_parse_json(raw)

  Correct

  try_parse_json returns NULL for strings that cannot be parsed.

• Dto_json(raw)

  Incorrect

  to_json converts values to JSON strings, the opposite direction.

parse_json returns an error when the string is not valid JSON, while try_parse_json returns NULL.

• Aexplode(order:items)

  Incorrect

  explode works on ARRAY and MAP types, not on a VARIANT.

• Bvariant_explode(order:items)

  Correct

  variant_explode returns pos, key and value columns, one row per array element or object field.

• Cschema_of_variant(order:items)

  Incorrect

  That returns a schema string, not rows.

• Dvariant_get(order, '$.items', 'string')

  Incorrect

  That extracts one value per row as a string.

variant_explode un-nests a VARIANT array or object into rows with pos, key and value. For arrays the key is NULL; variant_explode_outer keeps a NULL row when the input is not an array or object.

• Av:items[1].sku

  Incorrect

  Array indexes are zero-based, so [1] is the second item.

• Bv.items.sku

  Incorrect

  Dot notation on the column is for STRUCT fields, not VARIANT paths.

• Cv:items:sku

  Incorrect

  A field inside an array element needs the element index.

• Dv:items[0].sku

  Correct

  Colon notation follows field names with dots and array elements with zero-based brackets.

The : operator extracts a path from a VARIANT or JSON string; nested fields use dots and array elements use zero-based brackets.