獲取 mysql 中平均列的平均值

Question

我有一張存儲餐廳評級的桌子。 如下圖所示。

我試圖獲得我成功的所有這些列的平均值，但我也想要所有這些平均值的平均值作為主要平均值。

我嘗試了以下查詢，但平均評分為 3，這是不准確的。 我認為 mysql 正在向我返回最終結果的整數值。

return $this->db->select('((ambience + music + service + value_for_money + cleanliness + sanitary + view)/7) as rating, AVG(ambience) as ambience, AVG(music) as music, AVG(service) as service,AVG(value_for_money) as value_for_money, AVG(cleanliness) as cleanliness, AVG(sanitary) as sanitary, AVG(view) as view' )
        ->where('restaurant_id',$restaurantId)
        ->get('restaurant_ratings')
        ->row_array();

當我運行上述查詢時，我得到 3 作為評級字段的平均值。

實際結果為 3.42。

請幫助我了解我做錯了什么以及可以做些什么來獲得准確的結果。 謝謝

Answer 1

只需添加AVG即可計算評分：

$query = 
    'AVG((
        ambience + 
        music + 
        service + 
        value_for_money + 
        cleanliness + 
        sanitary + 
        view
    )/7) as rating, 
    AVG(ambience) as ambience, 
    AVG(music) as music, 
    AVG(service) as service,
    AVG(value_for_money) as value_for_money, 
    AVG(cleanliness) as cleanliness, 
    AVG(sanitary) as sanitary, 
    AVG(view) as view';

return $this->db
            ->select($query)
            ->where('restaurant_id',$restaurantId)
            ->get('restaurant_ratings')
            ->row_array();