JSON_OBJECT

Purpose

The SQL/JSON function JSON_OBJECT takes as its input one or more property key-value pairs. It returns a JSON object that contains an object member for each of those key-value pairs.

[KEY] string VALUE expr

Use this clause to specify a property key-value pair.

  • KEY is optional and is provided for semantic clarity.

  • Use string to specify the property key name as a case-sensitive text literal.

  • Use expr to specify the property value. For expr, you can specify any expression that evaluates to a SQL numeric literal, text literal, date, or timestamp. The date and timestamp data types are printed in the generated JSON object or array as JSON strings following the ISO date format. If expr evaluates to a numeric literal, then the resulting property value is a JSON number value; otherwise, the resulting property value is a case-sensitive JSON string value enclosed in double quotation marks.

FORMAT JSON

Use this optional clause to indicate that the input string is JSON, and will therefore not be quoted in the output.

JSON_on_null_clause

Use this clause to specify the behavior of this function when expr evaluates to null.

  • NULL ON NULL - When NULL ON NULL is specified, then a JSON NULL value is used as a value for the given key.
    SELECT JSON_OBJECT('key1' VALUE NULL)  evaluates to  {"key1" :  null}
  • ABSENT ON NULL - If you specify this clause, then the function omits the property key-value pair from the JSON object.

JSON_returning_clause

Use this clause to specify the type of return value. One of :

  • VARCHAR2 specifying the size as a number of bytes or characters. The default is bytes. If you omit this clause, or specify the clause without specifying the size value, then JSON_ARRAY returns a character string of type VARCHAR2(4000). Refer to VARCHAR2 Data Type for more information. Note that when specifying the VARCHAR2 data type elsewhere in SQL, you are required to specify a size. However, in the JSON_returning_clause you can omit the size.

  • CLOB to return a character large object containing single-byte or multi-byte characters.

  • BLOB to return a binary large object of the AL32UTF8 character set.

STRICT

Specify the STRICT clause to verify that the output of the JSON generation function is correct JSON. If the check fails, a syntax error is raised.

Example 1: Output string appears within quotes, because FORMAT JSON is not used

SELECT JSON_OBJECT ('name' value 'Foo') FROM DUAL
Output:
JSON_OBJECT('NAME'VALUE'FOO'FORMATJSON)
-------------------------------------------------
{"name":"Foo"}

Example 2: No quotes around output string when FORMAT JSON is used.

SELECT JSON_OBJECT ('name' value 'Foo' FORMAT JSON ) FROM DUAL
Output:
JSON_OBJECT('NAME'VALUE'FOO'FORMATJSON)
-------------------------------------------------
{"name":Foo}

Example 3:JSON Syntax error when FORMAT JSON STRICT is used.

SELECT JSON_OBJECT ('name' value 'Foo' FORMAT JSON STRICT ) FROM DUAL
Output:
ORA-40441: JSON syntax error

WITH UNIQUE KEYS

Specify WITH UNIQUE KEYS to guarantee that generated JSON objects have unique keys.

Examples

The following example returns JSON objects that each contain two property key-value pairs:

SELECT JSON_OBJECT (
    KEY 'deptno' VALUE d.department_id,
    KEY 'deptname' VALUE d.department_name 
    ) "Department Objects"
  FROM departments d
  ORDER BY d.department_id;

Department Objects
----------------------------------------
{"deptno":10,"deptname":"Administration"}
{"deptno":20,"deptname":"Marketing"}
{"deptno":30,"deptname":"Purchasing"}
{"deptno":40,"deptname":"Human Resources"}
{"deptno":50,"deptname":"Shipping"}
. . .