How to calculate the length of a JSON (JavaScript Object Notation) value using the JSON_LENGTH() function?

JSON_LENGTH(json, path) is a MySQL built-in function that calculates the length of a JSON (JavaScript Object Notation) value at the given path location using the following rules:

• The length of a JSON scalar is 1.
• The length of a JSON array or object is the number of members.

For example:

SELECT JSON_LENGTH('[1, 2, {"a": 3}]');
  -- +---------------------------------+
  -- | JSON_LENGTH('[1, 2, {"a": 3}]') |
  -- +---------------------------------+
  -- |                               3 |
  -- +---------------------------------+

SELECT JSON_LENGTH('{"a": 1, "b": {"c": 30}}');
  -- +-----------------------------------------+
  -- | JSON_LENGTH('{"a": 1, "b": {"c": 30}}') |
  -- +-----------------------------------------+
  -- |                                       2 |
  -- +-----------------------------------------+

SELECT JSON_LENGTH('{"a": 1, "b": {"c": 30}}', '$.b');
  -- +------------------------------------------------+
  -- | JSON_LENGTH('{"a": 1, "b": {"c": 30}}', '$.b') |
  -- +------------------------------------------------+
  -- |                                              1 |
  -- +------------------------------------------------+

Reference information of the JSON_LENGTH() function:

JSON_LENGTH(json, path): int
  Calculates the length of a JSON (JavaScript Object Notation) value
  at the given path location by counting its members.

Arguments, return value and availability:
  json: Required. The JSON value to be observed.
  path: Optional. The default is '$'.
    The location of a child member to be measured.
  int: Return value. The length of the JSON value.
  Available since MySQL 5.7.

⇒ JSON_MERGE() - Synonym for JSON_MERGE_PRESERVE()

⇐ JSON_KEYS() - Exacting Keys from JSON Object

⇑ MySQL Functions on JSON Values

⇑⇑ MySQL Function References