set @@default_storage_engine = IF(2=1,'MyISAM','InnoDB');

Query OK, 0 rows affected, 1 warning (0.00 sec)

show warnings;

+---------+------+---------------------------------------------+

| Level   | Code | Message                                     |

+---------+------+---------------------------------------------+

| Warning | 1292 | Truncated incorrect INTEGER value: 'InnoDB' |

+---------+------+---------------------------------------------+

1 row in set (0.00 sec)

select @@default_storage_engine;

+--------------------------+

| @@default_storage_engine |

+--------------------------+

| InnoDB                   |

+--------------------------+

1 row in set (0.00 sec)

set @@default_storage_engine = IF(2=2,'MyISAM','InnoDB');

Query OK, 0 rows affected, 1 warning (0.00 sec)

show warnings;

+---------+------+---------------------------------------------+

| Level   | Code | Message                                     |

+---------+------+---------------------------------------------+

| Warning | 1292 | Truncated incorrect INTEGER value: 'MyISAM' |

+---------+------+---------------------------------------------+

1 row in set (0.00 sec)

select @@default_storage_engine;

+--------------------------+

| @@default_storage_engine |

+--------------------------+

| MyISAM                   |

+--------------------------+

1 row in set (0.00 sec)

set @@default_storage_engine = IF(2=1,'MyISAM','InnoDB');