Add values of two columns considering NULL values as zero in MySQL

For this, use COALESCE() function from MySQL. Let us first create a table −

mysql> create table DemoTable
-> (
-> Value1 int,
-> Value2 int
-> );
Query OK, 0 rows affected (0.51 sec)

Insert some records in the table using insert command −

mysql> insert into DemoTable values(100,200);
Query OK, 1 row affected (0.27 sec)

mysql> insert into DemoTable values(NULL,90);
Query OK, 1 row affected (0.13 sec)

mysql> insert into DemoTable values(NULL,NULL);
Query OK, 1 row affected (0.12 sec)

mysql> insert into DemoTable values(600,NULL);
Query OK, 1 row affected (0.12 sec)

Display all records from the table using select statement −

mysql> select *from DemoTable;

Output

This will produce the following output −

+--------+--------+
| Value1 | Value2 |
+--------+--------+
| 100    | 200    |
| NULL   | 90     |
| NULL   | NULL   |
| 600    | NULL   |
+--------+--------+
4 rows in set (0.00 sec)

Following is the query to treat NULL as zero and add values from two columns −

mysql> SELECT COALESCE(Value1, 0) + COALESCE(Value2, 0) AS Sum from DemoTable;

Output

This will produce the following output −

+------+
| Sum  |
+------+
| 300  |
| 90   |
| 0    |
| 600  |
+------+
4 rows in set (0.00 sec)