Documentation Home
MySQL 8.0 Reference Manual
Related Documentation Download this Manual
PDF (US Ltr) - 38.5Mb
PDF (A4) - 38.5Mb
PDF (RPM) - 33.3Mb
HTML Download (TGZ) - 8.1Mb
HTML Download (Zip) - 8.2Mb
HTML Download (RPM) - 7.0Mb
Man Pages (TGZ) - 134.2Kb
Man Pages (Zip) - 190.2Kb
Info (Gzip) - 3.4Mb
Info (Zip) - 3.4Mb
Excerpts from this Manual

MySQL 8.0 Reference Manual  /  ...  /  Functions That Return JSON Value Attributes

12.16.5 Functions That Return JSON Value Attributes

The functions in this section return attributes of JSON values.

  • JSON_DEPTH(json_doc)

    Returns the maximum depth of a JSON document. Returns NULL if the argument is NULL. An error occurs if the argument is not a valid JSON document.

    An empty array, empty object, or scalar value has depth 1. A nonempty array containing only elements of depth 1 or nonempty object containing only member values of depth 1 has depth 2. Otherwise, a JSON document has depth greater than 2.

    mysql> SELECT JSON_DEPTH('{}'), JSON_DEPTH('[]'), JSON_DEPTH('true');
    +------------------+------------------+--------------------+
    | JSON_DEPTH('{}') | JSON_DEPTH('[]') | JSON_DEPTH('true') |
    +------------------+------------------+--------------------+
    |                1 |                1 |                  1 |
    +------------------+------------------+--------------------+
    mysql> SELECT JSON_DEPTH('[10, 20]'), JSON_DEPTH('[[], {}]');
    +------------------------+------------------------+
    | JSON_DEPTH('[10, 20]') | JSON_DEPTH('[[], {}]') |
    +------------------------+------------------------+
    |                      2 |                      2 |
    +------------------------+------------------------+
    mysql> SELECT JSON_DEPTH('[10, {"a": 20}]');
    +-------------------------------+
    | JSON_DEPTH('[10, {"a": 20}]') |
    +-------------------------------+
    |                             3 |
    +-------------------------------+
  • 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 or contains a * or ** wildcard.

    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:

  • JSON_VALID(val)

    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 |
    +---------------------+-----------------------+

User Comments
User comments in this section are, as the name implies, provided by MySQL users. The MySQL documentation team is not responsible for, nor do they endorse, any of the information provided here.
Sign Up Login You must be logged in to post a comment.