Official example of `CREATE JSON DUALITY VIEW` gives syntax error

According to [the release note of MySQL 9.4](https://dev.mysql.com/doc/relnotes/mysql/9.4/en/news-9-4-0.html) , *JSON duality views* are now supported. [*27.7.1 JSON Duality View Syntax*](https://dev.mysql.com/doc/refman/9.4/en/json-duality-views-syntax.html) shows this example:

CREATE TABLE customers (
    id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
    first_name VARCHAR(25),
    last_name VARCHAR(25),
    street VARCHAR(50),
    city VARCHAR(25),
    state CHAR(2),
    postcode CHAR(5),
    phone CHAR(10),
    email VARCHAR(50)
);

CREATE JSON DUALITY VIEW jdv_customers
  AS
    SELECT JSON_DUALITY_OBJECT( {
                '_id'   : c.id,
                'name'  : { 'fname' : c.first_name,
                            'lname' : c.last_name },
                'email' : c.email,
                'area'  : { 'city'  : c.city,
                            'state' : c.state }
                }
            )
FROM customers c;

Let me test that:

> SELECT VERSION();

+-----------+
| VERSION() |
+-----------+
| 9.4.0     |
+-----------+

> CREATE TABLE customers (
->     id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
->     first_name VARCHAR(25),
->     last_name VARCHAR(25),
->     street VARCHAR(50),
->     city VARCHAR(25),
->     state CHAR(2),
->     postcode CHAR(5),
->     phone CHAR(10),
->     email VARCHAR(50)
-> );

Query OK, 0 rows affected

> CREATE JSON DUALITY VIEW jdv_customers
->   AS
->     SELECT JSON_DUALITY_OBJECT( {
->                 '_id'   : c.id,
->                 'name'  : { 'fname' : c.first_name,
->                             'lname' : c.last_name },
->                 'email' : c.email,
->                 'area'  : { 'city'  : c.city,
->                             'state' : c.state }
->                 }
->             )
-> FROM customers c;

(1064, "You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '{\n                '_id'   : c.id,\n                'name'  : { 'fname' : c.first_' at line 3")

Why? Is this just a documentation bug or am I missing something? --- Edit: Reading [the documentation of JSON_DUALITY_OBJECT()](https://dev.mysql.com/doc/refman/9.4/en/json-creation-functions.html#function_json-duality-object) , it seems - {} of JSON_DUALITY_OBJECT( { ... } ) found in the example is incorrect. We must omit that. - Nested object { ... } found in the example is incorrect. Instead we have to specify a subquery like this:

'name' : (
      SELECT JSON_DUALITY_OBJECT(
        /* ... */
      )
      FROM customers AS c2
      WHERE c2.id = c.id
    ),

- And the documentation also says > If the table is projected multiple times, the set of columns projected must be consistent across all instances of the table projection. , meaning that top-level query and all of the subqueries must repeat the same set of columns. Following these rules gives:

CREATE JSON DUALITY VIEW jdv_customers AS
SELECT JSON_DUALITY_OBJECT(
  '_id'        : c.id,
  'first_name' : c.first_name,
  'last_name'  : c.last_name,
  'email'      : c.email,
  'city'       : c.city,
  'state'      : c.state,

  'name' : (
    SELECT JSON_DUALITY_OBJECT(
      'id'         : c2.id,         
      'first_name' : c2.first_name,
      'last_name'  : c2.last_name,
      'email'      : c2.email,
      'city'       : c2.city,
      'state'      : c2.state
    )
    FROM customers AS c2
    WHERE c2.id = c.id
  ),

  'area' : (
    SELECT JSON_DUALITY_OBJECT(
      'id'         : c3.id,
      'first_name' : c3.first_name,
      'last_name'  : c3.last_name,
      'email'      : c3.email,
      'city'       : c3.city,
      'state'      : c3.state
    )
    FROM customers AS c3
    WHERE c3.id = c.id
  )
)
FROM customers AS c;

This actually works (no syntax error) but is far more verbose then the official example. I even doubt if this is really an intended use-case of JSON duality view. Probably the intended use-case is not to project a single flat row to a nested JSON object but to directly map an inherently nested structure (e.g. that given by JOIN) to a JSON object without re-structuring.