SQL如何在另一个查询中访问和检查查询的元素？ （多到多）

Question

用户选择喜爱的商场，品牌和行业

我尝试显示对用户的收藏有效的广告系列。

表：Campaign（有商场和品牌），MallCampaign，Mall，Brand，Sector，User，Favorite

例如;用户选择 X，Y，Z （ Z：不包括阿迪达斯商店）商场; 阿迪达斯， Levi's ，维多利亚的秘密品牌; 鞋部门。因此，用户只能看到在 X，Y 商场中有效的 Adidas 广告系列。

如何组合这些查询？我应该使用JOIN还是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

我建议您使用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 
                  )

这澄清了查询的意图。而且，如果你有Favorite(UserId, FavorteItemType, FavoriteItemId)的索引，那么表现应该非常好。