In the previous article, I have shared basic about MySQL 5.7 new JSON Data Type.
MySQL 5.7 also introduced different types of JSON related function.
In this post, I am sharing a few of those important JSON function.

First, create a sample table with JSON data type:

CREATE TABLE tbl_TestJSON
(
	ID INTEGER PRIMARY KEY
	,DepartName VARCHAR(250)
	,EmployeeDetails JSON
	,Address JSON
);

Insert few valid JSON Data:

INSERT INTO tbl_TestJSON
VALUES 
(
	1
	,'Sales'
	,'{"firstName": "Anvesh", "lastName": "Patel"}'
	,'
	{"address" : 
		{ 
			"India": "Hyderabad"
			,"USA": "Newyork"
		}
	}'
)
,(
	2
	,'Production'
	,'{"firstName": "Neevan", "lastName": "Patel"}'
	,'
	{"address" : 
		{ 
			"India": "Ahmedabad"
			,"USA": "Washington DC"
		}
	}'
)
,(
	3
	,'Animation'
	,'{"firstName": "Eric", "lastName": "Lorn"}'
	,'
	{"address" : 
		{ 
			"India": "Mumbai"
			,"USA": "Chicago"
		}
	}'
);

JSON_EXTRACT(): To extract or search value in JSON.

SELECT JSON_EXTRACT(Address, "$.address.*") FROM tbl_TestJSON;
+--------------------------------------+
| JSON_EXTRACT(Address, "$.address.*") |
+--------------------------------------+
| ["Newyork", "Hyderabad"]             |
| ["Washington DC", "Ahmedabad"]       |
| ["Chicago", "Mumbai"]                |
+--------------------------------------+

SELECT JSON_EXTRACT(Address, "$.address.India") FROM tbl_TestJSON;
+------------------------------------------+
| JSON_EXTRACT(Address, "$.address.India") |
+------------------------------------------+
| "Hyderabad"                              |
| "Ahmedabad"                              |
| "Mumbai"                                 |
+------------------------------------------+

 SELECT JSON_EXTRACT(Address, "$**.USA") FROM tbl_TestJSON;
+----------------------------------+
| JSON_EXTRACT(Address, "$**.USA") |
+----------------------------------+
| ["Newyork"]                      |
| ["Washington DC"]                |
| ["Chicago"]                      |
+----------------------------------+

JSON_SEARCH(): Use to search key value path.
one: The search terminates after the first match and returns one path string
all: The search returns all matching path strings such that no duplicate paths are included.

SELECT JSON_SEARCH(Address,'one','Mumbai') FROM tbl_TestJSON; 
SELECT JSON_SEARCH(Address,'all','Mumbai') FROM tbl_TestJSON;

JSON_LENGTH():Use to check length of JSON document.

SELECT JSON_LENGTH (EmployeeDetails) FROM tbl_TestJSON;

JSON_TYPE(): Use to check type of JSON document.

SELECT JSON_TYPE (EmployeeDetails) FROM tbl_TestJSON;

JSON_KEYS(): Use to fetch list of JSON keys.

SELECT JSON_KEYS (EmployeeDetails) FROM tbl_TestJSON;

JSON_MERGE(): Use to merge JSON data.

SELECT JSON_MERGE('["Anvesh", 1]', '{"Name": "Anvesh"}');
+---------------------------------------------------+
| JSON_MERGE('["Anvesh", 1]', '{"Name": "Anvesh"}') |
+---------------------------------------------------+
| ["Anvesh", 1, {"Name": "Anvesh"}]                 |
+---------------------------------------------------+

JSON_ARRAY_APPEND(): Use to append any data into JSON document.

SELECT JSON_ARRAY_APPEND('["a", ["b", "c"], "d"]','$[1]','e');
+--------------------------------------------------------+
| JSON_ARRAY_APPEND('["a", ["b", "c"], "d"]','$[1]','e') |
+--------------------------------------------------------+
| ["a", ["b", "c", "e"], "d"]                            |
+--------------------------------------------------------+

SELECT JSON_ARRAY_APPEND('["a", ["b", "c"], "d"]','$[0]','g');
+--------------------------------------------------------+
| JSON_ARRAY_APPEND('["a", ["b", "c"], "d"]','$[0]','g') |
+--------------------------------------------------------+
| [["a", "g"], ["b", "c"], "d"]                          |
+--------------------------------------------------------+