MySQL错误代码1215：无法在ALTER TABLE：Mysql上添加外键约束

Question

I want to add foreign key Constraint on my existing tables(type InnoDB) ,I have two tables listed below:

tbl_users : [ user_id(INT,AUTO_INCREMENT), user_name,--- etc]
tbl_users_meta : [ user_meta_id(INT,AUTO_INCREMENT), user_id(INT),--- etc]

I have already created index 'user_id' on 'tbl_users_meta' listed below :

Here is my Query but i am getting (MySQL Error Code 1215: ) each time.what is the problem i can getting it ?

ALTER TABLE `tbl_users_meta` 
ADD  CONSTRAINT `fk users user_id`
FOREIGN KEY (`user_id`) REFERENCES 
`sanskrut`.`tbl_users`(`user_id`)
ON DELETE NO ACTION ON UPDATE CASCADE;

Answer 1

TRY with the same query you have writen with a small modification:

ALTER IGNORE TABLE `tbl_users_meta` 
ADD  CONSTRAINT `fk users user_id`
FOREIGN KEY (`user_id`) REFERENCES 
`sanskrut`.`tbl_users`(`user_id`)
ON DELETE NO ACTION ON UPDATE CASCADE;

Hope it'll work