The following query returns the value {"item1":1,"item2":2,"item3":3}.

SELECT JSON_QUERY('{"item1":1, "item2":2, "item3":3}', '$') AS JSONQUERY FROM DUMMY;
The following query returns the value [1].

SELECT JSON_QUERY('{"item1":1, "item2":2, "item3":3}', '$.item1' WITH WRAPPER ) AS JSONQUERY FROM DUMMY;