JSON_LENGTH( json_doc [, path ]) Returns the length of a JSON document, or, if a path argument is given, the length of the value within the document identified by the path. Returns NULL if any argument is NULL or the path argument does not identify a value in the document. An error occurs if the json_doc argument is not a valid JSON document or the path argument is not a valid path expression. The length of a document is determined as follows: The length of a scalar is 1. The length of an array is the number of array elements. The length of an object is the number of object members. The length does not count the length of nested arrays or objects.

mysql> SELECT JSON_LENGTH('[1, 2, {"a": 3}]');
+---------------------------------+
| JSON_LENGTH('[1, 2, {"a": 3}]') |
+---------------------------------+
|                               3 |
+---------------------------------+
mysql> SELECT JSON_LENGTH('{"a": 1, "b": {"c": 30}}');
+-----------------------------------------+
| JSON_LENGTH('{"a": 1, "b": {"c": 30}}') |
+-----------------------------------------+
|                                       2 |
+-----------------------------------------+
mysql> SELECT JSON_LENGTH('{"a": 1, "b": {"c": 30}}', '$.b');
+------------------------------------------------+
| JSON_LENGTH('{"a": 1, "b": {"c": 30}}', '$.b') |
+------------------------------------------------+
|                                              1 |
+------------------------------------------------+

JSON_TYPE( json_val ) Returns a utf8mb4 string indicating the type of a JSON value. This can be an object, an array, or a scalar type, as shown here:

mysql> SET @j = '{"a": [10, true]}';
mysql> SELECT JSON_TYPE(@j);
+---------------+
| JSON_TYPE(@j) |
+---------------+
| OBJECT        |
+---------------+
mysql> SELECT JSON_TYPE(JSON_EXTRACT(@j, '$.a'));
+------------------------------------+
| JSON_TYPE(JSON_EXTRACT(@j, '$.a')) |
+------------------------------------+
| ARRAY                              |
+------------------------------------+
mysql> SELECT JSON_TYPE(JSON_EXTRACT(@j, '$.a[0]'));
+---------------------------------------+
| JSON_TYPE(JSON_EXTRACT(@j, '$.a[0]')) |
+---------------------------------------+
| INTEGER                               |
+---------------------------------------+
mysql> SELECT JSON_TYPE(JSON_EXTRACT(@j, '$.a[1]'));
+---------------------------------------+
| JSON_TYPE(JSON_EXTRACT(@j, '$.a[1]')) |
+---------------------------------------+
| BOOLEAN                               |
+---------------------------------------+

JSON_TYPE() returns NULL if the argument is NULL :

mysql> SELECT JSON_TYPE(NULL);
+-----------------+
| JSON_TYPE(NULL) |
+-----------------+
| NULL            |
+-----------------+

An error occurs if the argument is not a valid JSON value:

mysql> SELECT JSON_TYPE(1);
ERROR 3146 (22032): Invalid data type for JSON data in argument 1
to function json_type; a JSON string or JSON type is required.

For a non- NULL , non-error result, the following list describes the possible JSON_TYPE() return values: Purely JSON types: OBJECT : JSON objects ARRAY : JSON arrays BOOLEAN : The JSON true and false literals NULL : The JSON null literal Numeric types: INTEGER : MySQL TINYINT , SMALLINT , MEDIUMINT and INT and BIGINT scalars DOUBLE : MySQL DOUBLE FLOAT scalars DECIMAL : MySQL DECIMAL and NUMERIC scalars Temporal types: DATETIME : MySQL DATETIME and TIMESTAMP scalars DATE : MySQL DATE scalars TIME : MySQL TIME scalars String types: STRING : MySQL utf8mb3 character type scalars: CHAR , VARCHAR , TEXT , ENUM , and Binary types: BLOB : MySQL binary type scalars including BINARY , VARBINARY , BLOB , and All other types: OPAQUE (raw bits) Returns 0 or 1 to indicate whether a value is valid JSON. Returns NULL if the argument is NULL .

mysql> SELECT JSON_VALID('{"a": 1}');
+------------------------+
| JSON_VALID('{"a": 1}') |
+------------------------+
|                      1 |
+------------------------+
mysql> SELECT JSON_VALID('hello'), JSON_VALID('"hello"');
+---------------------+-----------------------+
| JSON_VALID('hello') | JSON_VALID('"hello"') |
+---------------------+-----------------------+
|                   0 |                     1 |
+---------------------+-----------------------+