Set Default Value to a JSON Type Column in MySQL

To set default value, use the DEFAULT constraint as in the below syntax −

alter table yourTableName modify column yourColumnName JSON NOT NULL DEFAULT ( JSON_OBJECT() );

Let us create a table −

mysql> create table demo24
−> (
−> employee_information text
−> )
−> ;
Query OK, 0 rows affected (1.43 sec)

Here is the description of table. Following is the query −

mysql> desc demo24;

This will produce the following output −

+----------------------+------+------+-----+---------+-------+
| Field                | Type | Null | Key | Default | Extra |
+----------------------+------+------+-----+---------+-------+
| employee_information | text | YES  |     | NULL    |       | 
+----------------------+------+------+-----+---------+-------+
1 row in set (0.00 sec)

Following is the query to change it to JSON data type with default value −

mysql> alter table demo24 modify column employee_information JSON NOT NULL DEFAULT ( JSON_OBJECT() );
Query OK, 0 rows affected (3.03 sec)
Records: 0 Duplicates: 0 Warnings: 0

Now check the description of table. Following is the query −

mysql> desc demo24;

This will produce the following output −

+----------------------+------+------+-----+---------------+-------------------+
| Field                | Type | Null | Key | Default       | Extra             |
+----------------------+------+------+-----+---------------+-------------------+
| employee_information | json | NO   |     | json_object() | DEFAULT_GENERATED |
+----------------------+------+------+-----+---------------+-------------------+
1 row in set (0.00 sec)

Insert some records into the table with the help of insert command −

mysql> insert into demo24 values();;
Query OK, 1 row affected (0.10 sec)

Display records from the table using select statement −

mysql> select *from demo24;

This will produce the following output −

+----------------------+
| employee_information |
+----------------------+
| {}                   |
+----------------------+
1 row in set (0.00 sec)