本文介绍了如何在 SQLALchemy 中执行左连接?的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我有一个 SQL 查询,它在几个表上执行一系列左连接:
I have a SQL query which perfroms a series of left joins on a few tables:
SELECT <some attributes> FROM table1 t1 INNER JOIN table2 t2 ON attr = 1 AND attr2 = 1 LEFT JOIN table3 t3 ON t1.Code = t2.Code AND t3.Date_ = t1.Date_ LEFT JOIN tabl4 t4 ON t4.Code = t1.code AND t4.Date_ = t1.Date_到目前为止,我已经:
(sa.select([idc.c.Code]) .select_from( t1.join(t2, and_(t1.c.attr == 1, t2.c.attr2 = 1)) .join(t3, t3.c.Code == t1.c.Code)))但我不知道如何使加入成为 LEFT JOIN.
but I can't figure out how to make the join a LEFT JOIN.
推荐答案isouter=True 标志将产生一个 LEFT OUTER JOIN 与 相同>左加入.
The isouter=True flag will produce a LEFT OUTER JOIN which is the same as a LEFT JOIN.
使用您的代码:
(sa.select([idc.c.Code]) .select_from( t1.join(t2, and_(t1.c.attr == 1, t2.c.attr2 = 1)) .join(t3, t3.c.Code == t1.c.Code, isouter=True)))声明性示例:
session = scoped_session(sessionmaker()) session.query(Model).join(AnotherModel, AnotherModel.model_id == Model.id, isouter=True)更多推荐
如何在 SQLALchemy 中执行左连接?
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