MariaDB [test]> CREATE TABLE best.t2 (a INT PRIMARY KEY, b TEXT, FULLTEXT INDEX(b),

    -> FOREIGN KEY (a) REFERENCES t1(a)) ENGINE=InnoDB;

ERROR 1005 (HY000): Can't create table `best`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed")

MariaDB [test]> show warnings;

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

| Level   | Code | Message                                                                                                                                                                             |

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

| Warning |  150 | Create  table `best`.`t2` with foreign key constraint failed. Referenced table `best`.`t1` not found in the data dictionary near 'FOREIGN KEY (a) REFERENCES t1(a)) ENGINE=InnoDB'. |

| Error   | 1005 | Can't create table `best`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed")                                                                                          |

| Warning | 1215 | Cannot add foreign key constraint                                                                                                                                                   |

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

3 rows in set (0.00 sec)

Version: '10.2.19-MariaDB-debug-log'  socket: '/home/elenst/bld/10.2/mysql-test/var/tmp/mysqld.1.sock'  port: 16000  Source distribution

2018-10-24 12:26:00 139894668666624 [ERROR] InnoDB: Possible reasons:

2018-10-24 12:26:00 139894668666624 [ERROR] InnoDB: (1) Table rename would cause two FOREIGN KEY constraints to have the same internal name in case-insensitive comparison.

2018-10-24 12:26:00 139894668666624 [ERROR] InnoDB: (2) Table `test`.`t2` exists in the InnoDB internal data dictionary though MySQL is trying to rename table `best`.`t2` to it. Have you deleted the .frm file and not used DROP TABLE?

2018-10-24 12:26:00 139894668666624 [Note] InnoDB: Please refer to http://dev.mysql.com/doc/refman/5.7/en/innodb-troubleshooting.html for how to resolve the issue.

2018-10-24 12:26:00 139894668666624 [ERROR] InnoDB: If table `test`.`t2` is a temporary table #sql..., then it can be that there are still queries running on the table, and it will be dropped automatically when the queries end. You can drop the orphaned table inside InnoDB by creating an InnoDB table with the same name in another database and copying the .frm file to the current database. Then MySQL thinks the table exists, and DROP TABLE will succeed.