In the previous post, I discussed newly introduced JSON data type of PostgreSQL 9.4.

In this post, I am showing some of the basic JSON functions and operators which are also introduced by PostgreSQL 9.4.

Create sample table with jsonb data type and insert sample JSON data:

CREATE TABLE tbl_TestJSONData
(
	ID INTEGER PRIMARY KEY
	,DepartName VARCHAR(250)
	,EmployeeDetails JSONB
);

INSERT INTO tbl_TestJSONData
VALUES 
(
	1
	,'Sales'
	,'	
	{
		"firstName":"Anvesh"
		,"lastName":"Patel"
		,"gender":"Male"
		,"address":"Hyederabad"
		,"age":28
		,"role":
		[
			"admin"
			,"vendor"
		]
	}	    
	'
)
,(
	2
	,'Production'
	,'	
	{
		"firstName":"Neevan"
		,"lastName":"Patel"
		,"gender":"Male"
		,"address":"Hyederabad"
		,"age":20
		,"role":
		[
			"user"
			,"production"
		]
	}	    
	'
);

SELECT JSON Data using ‘->’ and ‘->>’ operators:

SELECT EmployeeDetails->'firstName' AS FirstName 
FROM tbl_TestJSONData;

/* Result as a JSON object. (Using ->)
firstname
----------
"Anvesh"
"Neevan"
*/

SELECT EmployeeDetails->>'firstName' AS FirstName 
FROM tbl_TestJSONData;

/* Result as a TEXT. (Using ->>)
firstname
----------
Anvesh
Neevan
*/

JSON Key value criteria in WHERE clause:

SELECT *FROM tbl_TestJSONData 
WHERE EmployeeDetails @> '{"age":28}'; 

/* one sales record is returned. */

JSON_EACH and JSONB_EACH Functions:
JSON_EACH and JSONB_EACH function to expand a JSONs data and nested JSONs are not expanded.
JSON_EACH for json data type and JSONB_EACH for jsonb data type.

SELECT jsonb_each(EmployeeDetails) AS JSONData FROM tbl_TestJSONData;

/*Result:

JSONData 
---------------
"(age,28)"
"(role,"[""admin"", ""vendor""]")"
"(gender,"""Male""")"
"(address,"""Hyederabad""")"
"(lastName,"""Patel""")"
"(firstName,"""Anvesh""")"
"(age,20)"
"(role,"[""user"", ""production""]")"
"(gender,"""Male""")"
"(address,"""Hyederabad""")"
"(lastName,"""Patel""")"
"(firstName,"""Neevan""")"

*/

JSON_OBJECT_KEYS and JSONB_OBJECT_KEYS Functions:
Returns all set of keys of JSON object and nested keys are not displayed.
JSON_OBJECT_KEYS is for json data type and JSONB_OBJECT_KEYS is for jsonb data type.

SELECT jsonb_object_keys(EmployeeDetails) AS JSONKeys
FROM tbl_TestJSONData;

/*Result:
age
role
gender
address
lastName
firstName
age
role
gender
address
lastName
firstName

*/

JSON_TYPEOF and JSONB_TYPEOF Functions:
This both functions respectively, for each data type and return the data type of the JSON keys.

SELECT jsonb_typeof(EmployeeDetails->'firstName') AS JSONKeyDataType
FROM tbl_TestJSONData;