//查询每天条数
type EveryDayNum struct {
    Day string `json:"day"`
    Num int64  `json:"num"`
}

func CountVisitorsEveryDay(toId string) []EveryDayNum {
    var results []EveryDayNum
    DB.Raw("select DATE_FORMAT(updated_at,'%Y-%m-%d') as day ,"+
        "count(*) as num from visitor where to_id=? group by day order by day desc limit 30",
        toId).Scan(&results)
    return results
}