How do I update NULL values in a field in MySQL?

Let us first create a table −

mysql> create table OrderDemo
   -> (
   -> OrderId int NOT NULL AUTO_INCREMENT PRIMARY KEY,
   -> OrderPrice int,
   -> OrderDatetime datetime
   -> );
Query OK, 0 rows affected (0.66 sec)

Example

Now you can insert some records in the table using insert command. The query is as follows −

mysql> insert into OrderDemo(OrderPrice,OrderDatetime) values(200,'2016-09-12');
Query OK, 1 row affected (0.24 sec)
mysql> insert into OrderDemo(OrderPrice,OrderDatetime) values(NULL,'2002-11-18');
Query OK, 1 row affected (0.26 sec)
mysql> insert into OrderDemo(OrderPrice,OrderDatetime) values(1000,'2017-12-28');
Query OK, 1 row affected (0.15 sec)

Display all records from the table using a select statement. The query is as follows −

mysql> select *from OrderDemo;

Output

+---------+------------+---------------------+
| OrderId | OrderPrice | OrderDatetime       |
+---------+------------+---------------------+
|       1 |        200 | 2016-09-12 00:00:00 |
|       2 |       NULL | 2002-11-18 00:00:00 |
|       3 |       1000 | 2017-12-28 00:00:00 |
+---------+------------+---------------------+
3 rows in set (0.00 sec)

Here is the query to add a row in OrderPrice column where OrderPrice is NULL i.e. updating the NULL −

mysql> update OrderDemo set OrderPrice = 6500 where OrderPrice IS NULL;
Query OK, 1 row affected (0.17 sec)
Rows matched: 1 Changed: 1 Warnings: 0

Now check the table record once again. The query is as follows −

mysql> select *from OrderDemo;

Output

+---------+------------+---------------------+
| OrderId | OrderPrice | OrderDatetime       |
+---------+------------+---------------------+
|       1 |        200 | 2016-09-12 00:00:00 |
|       2 |       6500 | 2002-11-18 00:00:00 |
|       3 |       1000 | 2017-12-28 00:00:00 |
+---------+------------+---------------------+
3 rows in set (0.00 sec)

The NULL value has been replaced with 6500.