如何在 SQLAlchemy 中为 MSSQL 设置模式？

Question

我目前这样做：

#!/usr/bin/env python

# 3rd party modules
from sqlalchemy import create_engine  # requires pymssql

# local modules
from config import cfg

connection_string = 'mssql+pymssql://{user}:{password}@{host}:{port}/{db}'

engine = create_engine(connection_string
                       .format(host=cfg['db']['host'],
                               db=cfg['db']['database'],
                               user=cfg['db']['user'],
                               password=cfg['db']['password'],
                               port=cfg['db']['port'],
                               schema=cfg['db']['schema']))

with engine.begin() as conn:
    sql = ('SELECT foo FROM bar;')
    rows = conn.execute(sql)
    print(rows)

但是我明白了

  File "/usr/local/lib/python3.5/dist-packages/sqlalchemy/engine/default.py", line 470, in do_execute
    cursor.execute(statement, parameters)
  File "pymssql.pyx", line 464, in pymssql.Cursor.execute (pymssql.c:7491)
sqlalchemy.exc.ProgrammingError: (pymssql.ProgrammingError) (208, b"Invalid object name 'bar'.DB-Lib error message 20018, severity 16:\nGeneral SQL Server error: Check messages from the SQL Server\n") [SQL: 'SELECT foo FROM bar;']

我认为问题在于我必须使用架构 exampleschema。我可以通过 DBeaver 使用相同的凭据访问架构 exampleschema 中列 foo 的 table bar。

但是当我将 /{schema} 添加到连接字符串时，我得到

sqlalchemy.exc.OperationalError: (pymssql.OperationalError)
    (18456,
     b"Login failed for user 'exampleuser'.DB-Lib error message 20018,
     severity 14:\nGeneral SQL Server error: Check messages from the SQL Server\nDB-Lib error message 20002,
     severity 9:\nAdaptive Server connection failed (192.168.123.456:1433)\n")

如何设置模式？

Answer 1

阅读这个 SO 问题 Possible to set default schema from connection string? 似乎无法 select 使用连接字符串的架构。

尝试全称：

sql = ('SELECT foo FROM exampleschema.bar;')

Answer 2

如果从数据库加载元数据并从元数据加载 table，则可以在 table 加载期间设置架构。

然后创建会话并查询table

from sqlalchemy import MetaData, Table
from sqlalchemy.orm import sessionmaker
table = Table({Table Name}, {metadata}, autoload=True, autoload_with={engine}, schema={Schema name})

Session = sessionmaker()
Session.configure(bind={engine})
session = Session()
query = session.query(table)

Answer 3

您还可以在 class 定义中指定架构名称（这不是您的具体情况，但我认为这是常见情况）。

例如，如果您有 table "dog" 到 "animal" 模式：

from sqlalchemy import Column, Integer, String
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()

class Notification(Base):
    __tablename__ = "dog"
    __table_args__ = {"schema": "animal"}
    id = Column(Integer, primary_key=True)
    name = Column(String)

如何在 SQLAlchemy 中为 MSSQL 设置模式？

How do I set the schema in SQLAlchemy for MSSQL?

python

sql-server

sqlalchemy

database-schema

pymssql