A brief discussion on whether MySQL can have a function similar to Oracle's nvl

Use ifnull instead of isnull

isnull is used to determine whether it is null. The return value is 1 for null or 0 for not null.

ifnull is equivalent to Oracle's nvl, and is used as follows

mysql> select ifnull(1,10);
+--------------+
| ifnull(1,10) |
+--------------+
| 1 |
+--------------+
1 row in set (0.00 sec)

mysql> select ifnull(null,10);
+-----------------+
| ifnull(null,10) |
+-----------------+
| 10 |
+-----------------+
1 row in set (0.00 sec)

The usage of isnull is as follows

mysql> select isnull(null);
+--------------+
| isnull(null) |
+--------------+
| 1 |
+--------------+
1 row in set (0.00 sec)

mysql> select isnull(1);
+-----------+
| isnull(1) |
+-----------+
| 0 |
+-----------+
1 row in set (0.00 sec)

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