参照定義

REFERENCES 表名 [ ( 単純列名 [ , 単純列名 ]* ) ]
[ ON DELETE {NO ACTION | RESTRICT | CASCADE | SET NULL}]
   [ ON UPDATE {NO ACTION | RESTRICT }]
|
[ ON UPDATE {NO ACTION | RESTRICT }] [ ON DELETE
   {NO ACTION | RESTRICT | CASCADE | SET NULL}] 
関連資料
列毎の制約
表ごとの制約
検索条件