Oracle select JSON column as key / value table [duplicate] - json

Question

This question already has an answer here:
Query json dictionary data in SQL
(1 answer)
Closed 1 year ago.
In Oracle 12c, having a column with JSON data in this format:
{
"user_name": "Dave",
"phone_number": "13326415",
"married": false,
"age": 18
}
How can I select it in this format:
key val
-------------- ----------
"user_name" "Dave"
"phone_number" "13326415"
"married" "false"
"age" "18"

Answer 1

As stated in the comment, there is no way to get the keys of a JSON object using just SQL. With PL/SQL you can create a pipelined function to get the information you need. Below is a very simple pipelined function that will get the keys of a JSON object and print the type each key is, as well as the key name and the value.
First, you will need to create the types that will be used by the function
CREATE OR REPLACE TYPE key_value_table_rec FORCE AS OBJECT
(
TYPE VARCHAR2 (100),
key VARCHAR2 (200),
VALUE VARCHAR2 (200)
);
/
CREATE OR REPLACE TYPE key_value_table_t AS TABLE OF key_value_table_rec;
/
Next, create the pipelined function that will return the information in the format of the types defined above.
CREATE OR REPLACE FUNCTION get_key_value_table (p_json CLOB)
RETURN key_value_table_t
PIPELINED
AS
l_json json_object_t;
l_json_keys json_key_list;
l_json_element json_element_t;
BEGIN
l_json := json_object_t (p_json);
l_json_keys := l_json.get_keys;
FOR i IN 1 .. l_json_keys.COUNT
LOOP
l_json_element := l_json.get (l_json_keys (i));
PIPE ROW (key_value_table_rec (
CASE
WHEN l_json_element.is_null THEN 'null'
WHEN l_json_element.is_boolean THEN 'boolean'
WHEN l_json_element.is_number THEN 'number'
WHEN l_json_element.is_timestamp THEN 'timestamp'
WHEN l_json_element.is_date THEN 'date'
WHEN l_json_element.is_string THEN 'string'
WHEN l_json_element.is_object THEN 'object'
WHEN l_json_element.is_array THEN 'array'
ELSE 'unknown'
END,
l_json_keys (i),
l_json.get_string (l_json_keys (i))));
END LOOP;
RETURN;
EXCEPTION
WHEN OTHERS
THEN
CASE SQLCODE
WHEN -40834
THEN
--JSON format is not valid
NULL;
ELSE
RAISE;
END CASE;
END;
/
Finally, you can call the pipelined function from a SELECT statement
SELECT * FROM TABLE (get_key_value_table (p_json => '{
"user_name": "Dave",
"phone_number": "13326415",
"married": false,
"age": 18
}'));
TYPE KEY VALUE
__________ _______________ ___________
string user_name Dave
string phone_number 13326415
boolean married false
number age 18
If your JSON values are stored in a column in a table, you can view the keys/values using CROSS JOIN
WITH
sample_table (id, json_col)
AS
(SELECT 1, '{"key1":"val1","key_obj":{"nested_key":"nested_val"},"key_bool":false}'
FROM DUAL
UNION ALL
SELECT 2, '{"key3":3.14,"key_arr":[1,2,3]}' FROM DUAL)
SELECT t.id, j.*
FROM sample_table t CROSS JOIN TABLE (get_key_value_table (p_json => t.json_col)) j;
ID TYPE KEY VALUE
_____ __________ ___________ ________
1 string key1 val1
1 object key_obj
1 boolean key_bool false
2 number key3 3.14
2 array key_arr