MYSQL - ne peut pas être en mesure de créer étrangère clé

Question

Lorsque j'exécute la requête en dessous renvoie une erreur,

alter table `ttis`.`users` 
add constraint `FK_Role_ID` FOREIGN KEY (`ROLE_ID`) REFERENCES `roles` (`ROLE_ID`) 

Erreur:

Error Code : 1005 
Can't create table 'ttis.#sql-9c_8a' (errno: 150) 

Answer 1

Jetez un oeil à ce poste: 13.6.4.4. FOREIGN KEY Constraints et la recherche de "150". Il est dit ici:

If you re-create a table that was dropped, it must have a definition that conforms to the foreign key constraints referencing it. It must have the right column names and types, and it must have indexes on the referenced keys, as stated earlier. If these are not satisfied, MySQL returns error number 1005 and refers to error 150 in the error message.

If MySQL reports an error number 1005 from a CREATE TABLE statement, and the error message refers to error 150, table creation failed because a foreign key constraint was not correctly formed. Similarly, if an ALTER TABLE fails and it refers to error 150, that means a foreign key definition would be incorrectly formed for the altered table. You can use SHOW ENGINE INNODB STATUS to display a detailed explanation of the most recent InnoDB foreign key error in the server.