MySQL 5.7 JSON type usage details

CREATE TABLE json_test( 
id INT, 
person_desc TEXT 
)ENGINE INNODB;

NSERT INTO json_test VALUES (1,'{ 
  "programmers": [{ 
    "firstName": "Brett", 
    "lastName": "McLaughlin", 
    "email": "aaaa" 
  }, { 
    "firstName": "Jason", 
    "lastName": "Hunter", 
    "email": "bbbb" 
  }, { 
    "firstName": "Elliotte", 
    "lastName": "Harold", 
    "email": "cccc" 
  }], 
  "authors": [{ 
    "firstName": "Isaac", 
    "lastName": "Asimov", 
    "genre": "sciencefiction" 
  }, { 
    "firstName": "Tad", 
    "lastName": "Williams", 
    "genre": "fantasy" 
  }, { 
    "firstName": "Frank", 
    "lastName": "Peretti", 
    "genre": "christianfiction" 
  }], 
  "musicians": [{ 
    "firstName": "Eric", 
    "lastName": "Clapton", 
    "instrument": "guitar" 
  }, { 
    "firstName": "Sergei", 
    "lastName": "Rachmaninoff", 
    "instrument": "piano" 
  }] 
}');

ALTER TABLE json_test MODIFY person_desc json;

mysql> SELECT id,json_keys(person_desc) as "keys" FROM json_test\G 
*************************** 1. row *************************** 
 id: 1 
keys: ["authors", "musicians", "programmers"] 
 row in set (0.00 sec)

mysql> SELECT json_extract(AUTHORS,'$.lastName[0]') AS 'name', AUTHORS FROM 
  -> ( 
  -> SELECT id,json_extract(person_desc,'$.authors[0][0]') AS "authors" FROM json_test 
  -> UNION ALL 
  -> SELECT id,json_extract(person_desc,'$.authors[1][0]') AS "authors" FROM json_test 
  -> UNION ALL 
  -> SELECT id,json_extract(person_desc,'$.authors[2][0]') AS "authors" FROM json_test 
  -> ) AS T1 
  -> ORDER BY NAME DESC\G 
*************************** 1. row *************************** 
  name: "Williams" 
AUTHORS: {"genre": "fantasy", "lastName": "Williams", "firstName": "Tad"} 
*************************** 2. row *************************** 
  name: "Peretti" 
AUTHORS: {"genre": "christianfiction", "lastName": "Peretti", "firstName": "Frank"} 
*************************** 3. row *************************** 
  name: "Asimov" 
AUTHORS: {"genre": "sciencefiction", "lastName": "Asimov", "firstName": "Isaac"} 
3 rows in set (0.00 sec)

mysql> SELECT 
  -> json_extract(AUTHORS,'$.firstName[0]') AS "firstname", 
  -> json_extract(AUTHORS,'$.lastName[0]') AS "lastname", 
  -> json_extract(AUTHORS,'$.genre[0]') AS "genre" 
  -> FROM 
  -> ( 
  -> SELECT id,json_extract(person_desc,'$.authors[0]') AS "authors" FROM json 
_test 
  -> ) AS T\G 
*************************** 1. row *************************** 
firstname: "Isaac" 
 lastname: "Asimov" 
  genre: "sciencefiction" 
 row in set (0.00 sec)

mysql> UPDATE json_test 
  -> SET person_desc = json_remove(person_desc,'$.authors')\G 
Query OK, 1 row affected (0.01 sec) 
Rows matched: 1 Changed: 1 Warnings: 0

mysql> SELECT json_contains_path(person_desc,'all','$.authors') as authors_exist 
s FROM json_test_G 
*************************** 1. row *************************** 
authors_exists: 0 
 row in set (0.00 sec)