SQL如何到達並檢查另一個查詢中的查詢元素？ （許多一對多）

Question

用戶選擇最喜歡的商場，品牌和行業

我試圖表明這是有效的用戶的最愛活動。

表：運動（具有商場及品牌），MallCampaign，購物中心，品牌，扇區，用戶，最喜歡的

例如;用戶選擇X，Y，Z（Z：不包括阿迪達斯店）商場; 阿迪達斯,李維斯,維多利亞的祕密品牌; 鞋子部門。所以用戶應該只看到阿迪達斯的活動，這是有效的X，Y商場。

如何結合這些查詢？我應該使用JOIN還是IF EXIST？

SELECT mc.CampaignId, c.CampaignTitle 
    FROM MallCampaign mc 
    JOIN Mall m ON m.MallId = mc.MallId 
    JOIN Campaign c ON c.CampaignId = mc.CampaignId 
    JOIN Brand b ON b.BrandId = c.BrandId 


    SELECT FavoriteItemId AS FavoriteMalls 
    FROM Favorite 
    WHERE UserId = @UserId AND FavoriteItemType=1 

    SELECT FavoriteItemId AS FavoriteBrands 
    FROM Favorite 
    WHERE UserId = @UserId AND FavoriteItemType=3 

    SELECT FavoriteItemId AS FavoriteSectors 
    FROM Favorite 
    WHERE UserId = @UserId AND FavoriteItemType=2 

Answer 1

我會建議你使用in：

SELECT mc.CampaignId, c.CampaignTitle 
FROM MallCampaign mc 
where mallid in (SELECT FavoriteItemId AS FavoriteMalls 
       FROM Favorite 
       WHERE UserId = @UserId AND FavoriteItemType=1 
       ) and 
     brandId in (SELECT FavoriteItemId AS FavoriteBrands 
        FROM Favorite 
        WHERE UserId = @UserId AND FavoriteItemType=3 
       ) and 
     sectorid in (SELECT FavoriteItemId AS FavoriteSectors 
        FROM Favorite 
        WHERE UserId = @UserId AND FavoriteItemType=2 
       ) 

這明確了查詢的意圖。而且，如果你有一個Favorite(UserId, FavorteItemType, FavoriteItemId)的指數，那麼表現應該相當不錯。