Bug 122520 foreign key constraints

[Dan Lewis]

When upgrading MySQL 8.0.13 from 5.7, a problem occurs if any of the 
foreign key restraints contains a primary key with one or more capital 
letters in it. MySQL converts any capital letters to lower case in the 
foreign key restraint while still recognizing the primary key with its 
capital.

For example: the primary key is Primary_id and its foreign key is 
foreign_id. In practice, the restraint links these two fields: 
primary_id and foreign_id respectively. Since primary_id contains no 
data, the related tables can not be used in a query.

A warning of some type should be made stating that primary keys are not 
to have any capital letters in it.

Dan