SQLAlchemy的LEFT JOIN WHERE子句被轉換成零和一

Howdie做，SQLAlchemy的LEFT JOIN WHERE子句被轉換成零和一

我有以下SQL，我正在轉換爲SQLAlchemy的：

select t1.`order_id`, t1.`status_type` 
from `tracking_update` AS t1 LEFT JOIN `tracking_update` AS t2 
ON (t1.`order_id` = t2.`order_id` AND t1.`last_updated` < t2.`last_updated`) 
where t1.`order_id` = '21757'and t2.`last_updated` IS NULL

的SQL只是返回的最新跟蹤更新訂單ID 21757.我正在通過左連接回到同一個表來完成此操作。爲了做到這一點，我首先走樣表：

 tUAlias1 = aliased(TrackingUpdate) 
     tUalias2 = aliased(TrackingUpdate)

到目前爲止，這是我爲我轉換爲SQLAlchemy的：

tracking_updates = db.session.query(tUAlias1.order_id, tUAlias1.status_type).\ 
      outerjoin(tUalias2, (tUAlias1.order_id == tUalias2.order_id) & (tUAlias1.last_updated < tUalias2.last_updated)).\ 
      filter(and_(tUAlias1.order_id == '21757', tUalias2.last_updated is None))

這是SQLAlchemy的結果經由日誌在服務器上執行的代碼：

SELECT tracking_update_1.order_id AS tracking_update_1_order_id, tracking_update_1.status_type AS tracking_update_1_status_type 
FROM tracking_update AS tracking_update_1 LEFT OUTER JOIN tracking_update AS tracking_update_2 ON tracking_update_1.order_id = tracking_update_2.order_id AND tracking_update_1.last_updated < tracking_update_2.last_updated 
WHERE 0 = 1

正如你可以看到，過濾器（WHERE子句）現在是0 = 1

現在，如果我刪除and_聲明，並嘗試兩個過濾器，像這樣：

tracking_updates = db.session.query(tUAlias1.order_id, tUAlias1.status_type).\ 
      outerjoin(tUalias2, (tUAlias1.order_id == tUalias2.order_id) & (tUAlias1.last_updated < tUalias2.last_updated)).\ 
      filter(tUAlias1.order_id == '21757').filter(tUalias2.last_updated is None)

我收到了同樣的結果。我知道SQL本身很好，因爲我可以通過MySQL工作臺來運行它。

當SQL直接運行，我會收到以下

order ID | Status 
21757  D

另外，如果我刪除tUalias2.last_updated是無，我居然收到了一定的效果，但它們都是不正確的。這是SQL日誌中：

Python代碼

tracking_updates = db.session.query(tUAlias1.order_id, tUAlias1.status_type).\ 
      outerjoin(tUalias2, (tUAlias1.order_id == tUalias2.order_id) & (tUAlias1.last_updated < tUalias2.last_updated)).\ 
      filter(tUAlias1.order_id == '21757')

SQLAlchemy的運行：

SELECT tracking_update_1.order_id AS tracking_update_1_order_id, tracking_update_1.status_type AS tracking_update_1_status_type 
FROM tracking_update AS tracking_update_1 LEFT OUTER JOIN tracking_update AS tracking_update_2 ON tracking_update_1.order_id = tracking_update_2.order_id AND tracking_update_1.last_updated < tracking_update_2.last_updated 
WHERE tracking_update_1.order_id = '21757'

任何想法？

來源

2016-01-06 Jimmy

Howdie做，

我想通了

Python的 '是' 我發現了這一點要歸功於以下S/O問題運營商沒有發揮好與SQLAlchemy的

：

Selecting Null values SQLAlchemy

因爲我已經更新了我的查詢到以下幾點：

tracking_updates = db.session.query(tUAlias1.order_id, tUAlias1.status_type).\ 
      outerjoin(tUalias2, (tUAlias1.order_id == tUalias2.order_id) & (tUAlias1.last_updated < tUalias2.last_updated)).\ 
      filter(tUAlias1.order_id == '21757').filter(tUalias2.last_updated == None)

來源

2016-01-06 20:41:23 Jimmy

SQLAlchemy的LEFT JOIN WHERE子句被轉換成零和一

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