MySQL error code 1452: Foreign key What's wrong (good long no longer repeat English haha ha)

I see a lot of the same solution here, okay, all the same, here's an article from the Linux commune. Http://www.linuxidc.com/Linux/2012-10/71821.htm, as for my own solution, I first clear the data index, and then delete the record, this time should be able to add foreign keys on the other side (you know what I mean, Is originally from A to B add foreign key, I this to add from B to a foreign key reverse operation the most invincible hahaha, I am still thinking that this operation and what is different, but the result is: successful implementation of the foreign Key Association. Of course, the data must be populated before the foreign keys and indexes are set.

MySQL error code 1452: Foreign key What's wrong (good long no longer repeat English haha ha)