CREATE TABLE klb_log (
  id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,log_comment varchar(512)
)

CREATE TABLE klb_log_food_maps (
  uid integer,did integer,PRIMARY KEY (uid,did),FOREIGN KEY (uid) references klb_log(id) ON DELETE CASCADE,FOREIGN KEY (did) references klb_food(id) ON DELETE CASCADE
)

CREATE TABLE klb_food (
  id integer,description varchar(255),PRIMARY KEY (id)
)

有没有理由为什么当我删除klb_log中的一行时，klb_log_food_maps中的行不会被删除？