Typecasting NULL to 0 in MySQL

You can typecast NULL to 0 with the help of IFNULL() function. The syntax is as follows −

select ifnull(yourColumnName) as anyVariableName from yourTableName;

To understand the above concept, let us first create a table −

mysql> create table TypecastDemo
   −> (
      −> AccountNumber int
   −> );
Query OK, 0 rows affected (0.84 sec)

Let us insert some records with NULL value. The query to insert records is as follows −

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

mysql> insert into TypecastDemo values(1234);
Query OK, 1 row affected (0.14 sec)

mysql> insert into TypecastDemo values(9876);
Query OK, 1 row affected (0.14 sec)

mysql> insert into TypecastDemo values(6666);
Query OK, 1 row affected (0.16 sec)

mysql> insert into TypecastDemo values(NULL);
Query OK, 1 row affected (0.27 sec)

mysql> insert into TypecastDemo values(NULL);
Query OK, 1 row affected (0.36 sec)

mysql> insert into TypecastDemo values(3214);
Query OK, 1 row affected (0.34 sec)

Now you can display all the records with the help of select statement. The query is as follows −

mysql> select *from TypecastDemo;

The following is the output −

+---------------+
| AccountNumber |
+---------------+
|          NULL |
|          1234 |
|          9876 |
|          6666 |
|          NULL |
|          NULL |
|          3214 |
 +---------------+
7 rows in set (0.00 sec)

Apply the syntax we saw above to typecast the NULL to 0. The query is as follows −

mysql> select ifnull(AccountNumber,0) as TypeCastNullToZero from TypecastDemo;

The following is the output −

+--------------------+
| TypeCastNullToZero |
+--------------------+
|                  0 |
|               1234 |
|               9876 |
|               6666 |
|                  0 |
|                  0 |
|               3214 |
+--------------------+
7 rows in set (0.00 sec)

Suppose you want more than one column then you can use COALESCE.