postgresql - 如何修复 "missing FROM-clause entry for table"错误

Question

我正在尝试根据游戏 ID 获取平台名称。

我有如下三个表，我正在尝试连接它们以获得所需的结果:

      Games

Id | .....| .....|
---|------ ------|
1  | .    | .    |
2  | .    | .    |
3  | .    | .    |
4  | .    | .    |

      Game_Platforms

Id |....|game_id| platform_id|...|
---------------------------------
1  | .  | 1     |   1        |.. |
2  | .  | 1     |   2        |.. |
3  | .  | 3     |   3        |.. |
.. | .  | 4     |   4        |.. |

    Platforms
Id| ...|...| name    |
---------------------|
1 | .  | . | iOS     |
2 | .  | . | Android |
3 | .  | . | Windows |
4 | .  | . | SteamOS |

type Platforms struct {
   Name string
}

var name []Platforms

query = postgres.Db().Select("name").
        Joins("JOIN games ON games.id = game_platforms.game_id").
        Joins("JOIN game_platforms ON game_platforms.platform_id = platforms.id").
        Where("games.id = 1").Find(&name)

我希望获得平台名称，但出现错误:

pq: missing FROM-clause entry for table "game_platforms"

我认为我写的 Joins 命令不正确，但看起来合乎逻辑，也许我错了。

Answer 1

您的查询缺少 FROM 子句。

我假设您想从 platforms 表中选择数据。如果是，那么(根据您的代码)您应该首先加入 game_platforms，然后加入 games。

query = postgres.Db().Select("name").
    Find("platforms"). // <------ this one
    Joins("JOIN game_platforms ON game_platforms.platform_id = platforms.id").
    Joins("JOIN games ON games.id = game_platforms.game_id").
    Where("games.id = 1").Find(&name)