MySQL foreign key contraint allow nulls not working

MySQL foreign key contraint allow nulls not working

References

Reference NO 1

http://stackoverflow.com/questions/15205540/mysql-foreign-key-contraint-allow-nulls-not-working

Reference NO 2

http://stackoverflow.com/questions/4046723/mysql-foreign-key-constraint-integer-column

Reference NO 3

http://dev.mysql.com/doc/en/innodb-foreign-key-constraints.html

Reference NO 4

http://social.msdn.microsoft.com/Forums/sqlserver/en-US/ce28c45c-1f84-46af-bd9e-474c7edb2367/action?threadDisplayName=null-values-in-foreign-keys-best-practice

Reference NO 5

http://wiki.navicat.com/wiki/index.php/Why_I_cannot_successfully_create_the_foreign_keys%3F

Reference NO 6

http://www.yiiframework.com/forum/index.php/topic/4758-solved-problem-with-foreign-key-on-null-fields/

Reference NO 7

http://www.informit.com/articles/article.aspx?p=30875&seqNum=8

Reference NO 8

#EANF#