我正在尝试使用sqlalchemy core api多次加入同一个表。
以下是代码:
import sqlparse
import sqlalchemy as sa
meta = sa.MetaData('sqlite:///:memory:')
a = sa.Table(
'a', meta,
sa.Column('id', sa.Integer, primary_key=True),
)
b = sa.Table(
'b', meta,
sa.Column('id', sa.Integer, primary_key=True),
sa.Column('x', sa.Integer, sa.ForeignKey(a.c.id)),
sa.Column('y', sa.Integer, sa.ForeignKey(a.c.id)),
)
meta.create_all()
x = b.alias('x')
y = b.alias('y')
query = (
sa.select(['*']).
select_from(a.join(x, a.c.id == x.c.x)).
select_from(a.join(y, a.c.id == y.c.y))
)
print(sqlparse.format(str(query), reindent=True))
最后一个语句产生以下输出:
SELECT *
FROM a
JOIN b AS x ON a.id = x.x,
a
JOIN b AS y ON a.id = y.y
如果我尝试执行此查询query.execute()
,我会收到错误:
sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) ambiguous column name: main.a.id [SQL: 'SELECT * \nFROM a JOIN b AS x ON a.id = x.x, a JOIN b AS y ON a.id = y.y']
问题是,如何摆脱, a
?如果我尝试执行:
engine.execute('''
SELECT *
FROM a
JOIN b AS x ON a.id = x.x
JOIN b AS y ON a.id = y.y
''')
工作正常。
答案 0 :(得分:6)
query = (
sa.select(['*']).
select_from(a
.join(x, a.c.id == x.c.x)
.join(y, a.c.id == y.c.y)
)
)