Error in foreign key constraint of table test/child:
there is no index in referenced table which would contain
the columns as the first columns, or the data types in the
referenced table do not match to the ones in table. Constraint:
,
  CONSTRAINT child_ibfk_1 FOREIGN KEY (parent_id) REFERENCES parent (parent_id)
The index in the foreign key in table is parent_id
See http://dev.mysql.com/doc/refman/5.0/en/innodb-foreign-key-constraints.html
for correct foreign key definition.