JSON_OBJECT¶

The JSON_OBJECT constructor creates a JSON object from relational data.

JSON_OBJECT (   [JSON key and value [{,JSON key and value}...]   [NULL|ABSENT ON NULL]   [WITH|WITHOUT UNIQUE [KEYS]]   [RETURNING datatype])

where:

JSON key and value

Specifies the values in the table that you want to use for key and value in the key:value pair, using the following form:

[KEY] name VALUE value | name:value

The value used for name must be a string. A maximum of 100 key:value pairs is allowed. The KEY keyword is optional and has no affect on the returned object.

NULL ON NULL | ABSENT ON NULL

Specifies how nulls are handled. NULL ON NULL uses the string “null” if the input value is null. ABSENT ON NULL omits this key:value pair from the returned object. Default is NULL ON NULL.

WITH UNIQUE [KEYS] | WITHOUT UNIQUE [KEYS]

WITH UNIQUE returns an error if the object created by JSON_OBJECT has duplicate keys in its key:value pairs. For example, {"Name":"Frank","Name":"Bob"} generates an error.

WITHOUT UNIQUE does not enforce unique keys but does not require them. Default is WITHOUT UNIQUE.

RETURNING datatype

Specifies the data type of the result. Any string data type is permitted. Default is varchar(4000).

JSON_OBJECT is typically used in a select. For example:

Assume a table emp that contains the following rows:

+-------------+----------+-------+|row          |name      | unit  |+-------------+----------+-------+|            1|Frank     | 1A    ||            2|Steve     | 2A    ||            1|Bob       | 1B    ||            2|null      | 2B    |+-------------+----------+-------+

SELECT JSON_OBJECT (KEY 'id' VALUE emp.row,             KEY 'name' VALUE emp.name) FROM emp;

returns four JSON objects:

{"id": 1, "name": "Frank"}{"id": 2, "name": "Steve"}{"id": 1, "name": "Bob"}{"id": 2, "name": null}

If ABSENT ON NULL was specified in the above query, the row corresponding to unit 2B would be omitted and the result would only contain three rows.