> create table ss (id integer primary key, struct TEXT);

> create table mm (id integer primary key, sss integer NOT null references ss(id), name TEXT, UNIQUE(sss, name));

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

> SHOW ENGINE INNODB STATUS;

...

LATEST FOREIGN KEY ERROR

------------------------

2025-02-14 09:29:24 0x7f3ab01ff6c0 Error in foreign key constraint of table `clang_struct`.`mm`:

Create  table `clang_struct`.`mm` with foreign key (sss) constraint failed. There is no index in the referenced table where the referenced columns appear as the first columns.------------

> show index from ss;

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

| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment | Ignored |

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

| ss    |          0 | PRIMARY  |            1 | id          | A         |           0 |     NULL | NULL   |      | BTREE      |         |               | NO      |

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

------------------------