使用别名自连接查询到 SQlAlchemy ORM

Question

我正在尝试将以下 SQL 查询转换为 SQlAlchemy 语句并遇到错误：

sqlalchemy.exc.InvalidRequestError: Don't know how to join to <AliasedInsp at 0x7fa9c5832be0; Task(Task)>. Please use the .select_from() method to establish an explicit left side, as well as providing an explicit ON clause if not present already to help resolve the ambiguity.

SQL 查询:

select t2.* 
from task as t1 
inner join task as t2 on t1.g_id  = t2.g_id  
where t1.id = 'task_id';

SQlAlchemy 语句：

table_a = aliased(Task)
table_b = aliased(Task)
query = (
    self.db.query(Task)
    .join(table_a, table_b).filter(table_b.group_id == table_a.group_id)
    .filter(table_a.id == task_id)
   )

尝试按照 SQL关于别名的 Alchemy 文档进行操作，但无法找出错误。

Answer 1

t1 = aliased(Task)
t2 = aliased(Task)

query = (
    self.db.query(t2)
    .select_from(t1)
    .join(t2, t2.g_id == t1.g_id)
    .filter(t1.id == task_id)
   )

使用别名自连接查询到 SQlAlchemy ORM

Self join query to SQlAlchemy ORM using alias

sql

sqlalchemy

python-3.x