我刚刚开始使用SQLAlchemy SQL表达式语言，并且我试图从现有表和文字值插入表值。我试图用SQL表达式语言模拟这个SQL语句：
INSERT INTO b_Customers
(CustomerID,
CustomerName,
CustomerType,
IsCurrent,
FirstObserved,
LastObserved)
SELECT CustomerID, CustomerName, CustomerType, 1, '2018-01-23', '2018-01-23'
FROM s_Customers
这是我正在运行的一些设置Python代码：
from datetime import datetime
from io import StringIO
import csv
from sqlalchemy import create_engine, Table, Column, Integer, Date, String, MetaData, ForeignKey, bindparam, text
from sqlalchemy.sql import select
from sqlalchemy.sql.expression import literal_column, literal
engine = create_engine('sqlite:///:memory:')
metadata = MetaData()
stage = Table('s_Customers', metadata,
Column('CustomerID', Integer, primary_key=True),
Column('CustomerName', String),
Column('CustomerType', String),
)
base = Table('b_Customers', metadata,
Column('CustomerID', Integer, primary_key=True),
Column('CustomerName', String),
Column('CustomerType', String),
Column('IsCurrent', Integer),
Column('FirstObserved', Date),
Column('LastObserved', Date),
)
metadata.create_all(engine)
insert_data = u'''CustomerID,CustomerName,CustomerType
1,Jannet,Preferred
2,Daniel,Regular
3,Casper,Regular'''
table_to_insert = StringIO(insert_data)
table_values = list(csv.DictReader(table_to_insert))
conn = engine.connect()
stmt = stage.insert().values(table_values)
conn.execute(stmt)
这就是我被困的地方：
stmt = base.insert().from_select(list(stage.columns) + [bindparam(1, 'IsCurrent'),
bindparam(datetime(2018, 1, 23), 'FirstObserved'),
bindparam(datetime(2018, 1, 23), 'LastObserved')],
stage)
conn.execute(stmt)
这是运行上述代码的堆栈跟踪：
---------------------------------------------------------------------------
KeyError Traceback (most recent call last)
<ipython-input-35-a3d52b22c83e> in <module>()
3 bindparam(datetime(2018, 1, 23), 'LastObserved')],
4 stage)
----> 5 conn.execute(stmt)
C:\Users\rdelgado\AppData\Local\Continuum\Anaconda2\Lib\site-packages\sqlalchemy\engine\base.pyc in execute(self, object, *multiparams, **params)
946 raise exc.ObjectNotExecutableError(object)
947 else:
--> 948 return meth(self, multiparams, params)
949
950 def _execute_function(self, func, multiparams, params):
C:\Users\rdelgado\AppData\Local\Continuum\Anaconda2\Lib\site-packages\sqlalchemy\sql\elements.pyc in _execute_on_connection(self, connection, multiparams, params)
267 def _execute_on_connection(self, connection, multiparams, params):
268 if self.supports_execution:
--> 269 return connection._execute_clauseelement(self, multiparams, params)
270 else:
271 raise exc.ObjectNotExecutableError(self)
C:\Users\rdelgado\AppData\Local\Continuum\Anaconda2\Lib\site-packages\sqlalchemy\engine\base.pyc in _execute_clauseelement(self, elem, multiparams, params)
1051 inline=len(distilled_params) > 1,
1052 schema_translate_map=self.schema_for_object
-> 1053 if not self.schema_for_object.is_default else None)
1054
1055 ret = self._execute_context(
<string> in <lambda>(self, bind, dialect, **kw)
C:\Users\rdelgado\AppData\Local\Continuum\Anaconda2\Lib\site-packages\sqlalchemy\sql\elements.pyc in compile(self, default, bind, dialect, **kw)
440 else:
441 dialect = default.StrCompileDialect()
--> 442 return self._compiler(dialect, bind=bind, **kw)
443
444 def _compiler(self, dialect, **kw):
C:\Users\rdelgado\AppData\Local\Continuum\Anaconda2\Lib\site-packages\sqlalchemy\sql\elements.pyc in _compiler(self, dialect, **kw)
446 Dialect."""
447
--> 448 return dialect.statement_compiler(dialect, self, **kw)
449
450 def __str__(self):
C:\Users\rdelgado\AppData\Local\Continuum\Anaconda2\Lib\site-packages\sqlalchemy\sql\compiler.pyc in __init__(self, dialect, statement, column_keys, inline, **kwargs)
451 # dialect.label_length or dialect.max_identifier_length
452 self.truncated_names = {}
--> 453 Compiled.__init__(self, dialect, statement, **kwargs)
454
455 if (
C:\Users\rdelgado\AppData\Local\Continuum\Anaconda2\Lib\site-packages\sqlalchemy\sql\compiler.pyc in __init__(self, dialect, statement, bind, schema_translate_map, compile_kwargs)
217 if self.can_execute:
218 self.execution_options = statement._execution_options
--> 219 self.string = self.process(self.statement, **compile_kwargs)
220
221 @util.deprecated("0.7", ":class:`.Compiled` objects now compile "
C:\Users\rdelgado\AppData\Local\Continuum\Anaconda2\Lib\site-packages\sqlalchemy\sql\compiler.pyc in process(self, obj, **kwargs)
243
244 def process(self, obj, **kwargs):
--> 245 return obj._compiler_dispatch(self, **kwargs)
246
247 def __str__(self):
C:\Users\rdelgado\AppData\Local\Continuum\Anaconda2\Lib\site-packages\sqlalchemy\sql\visitors.pyc in _compiler_dispatch(self, visitor, **kw)
79 raise exc.UnsupportedCompilationError(visitor, cls)
80 else:
---> 81 return meth(self, **kw)
82 else:
83 # The optimization opportunity is lost for this case because the
C:\Users\rdelgado\AppData\Local\Continuum\Anaconda2\Lib\site-packages\sqlalchemy\sql\compiler.pyc in visit_insert(self, insert_stmt, asfrom, **kw)
2032
2033 crud_params = crud._setup_crud_params(
-> 2034 self, insert_stmt, crud.ISINSERT, **kw)
2035
2036 if not crud_params and \
C:\Users\rdelgado\AppData\Local\Continuum\Anaconda2\Lib\site-packages\sqlalchemy\sql\crud.pyc in _setup_crud_params(compiler, stmt, local_stmt_type, **kw)
55 try:
56 if local_stmt_type in (ISINSERT, ISUPDATE):
---> 57 return _get_crud_params(compiler, stmt, **kw)
58 finally:
59 if should_restore:
C:\Users\rdelgado\AppData\Local\Continuum\Anaconda2\Lib\site-packages\sqlalchemy\sql\crud.pyc in _get_crud_params(compiler, stmt, **kw)
130 compiler, stmt, parameters,
131 _getattr_col_key, _column_as_key,
--> 132 _col_bind_name, check_columns, values, kw)
133 else:
134 _scan_cols(
C:\Users\rdelgado\AppData\Local\Continuum\Anaconda2\Lib\site-packages\sqlalchemy\sql\crud.pyc in _scan_insert_from_select_cols(compiler, stmt, parameters, _getattr_col_key, _column_as_key, _col_bind_name, check_columns, values, kw)
211
212 cols = [stmt.table.c[_column_as_key(name)]
--> 213 for name in stmt.select_names]
214
215 compiler._insert_from_select = stmt.select
C:\Users\rdelgado\AppData\Local\Continuum\Anaconda2\Lib\site-packages\sqlalchemy\util\_collections.pyc in __getitem__(self, key)
192
193 def __getitem__(self, key):
--> 194 return self._data[key]
195
196 def __delitem__(self, key):
KeyError: 1
我也尝试过使用literal（）和literal_column（），这些都没有成功。
感谢您的帮助！
答案 0 :(得分：0)
我知道了。我必须创建另一个可选择的文本列，然后从中选择：
stage_w_columns = select(list(stage.columns) + [literal(1).label('IsCurrent'),
literal(datetime(2018, 1, 23)).label('FirstObserved'),
literal(datetime(2018, 1, 23)).label('LastObserved')])
stmt = base.insert().from_select(stage_w_columns.columns, stage_w_columns)
conn.execute(stmt)
感谢路易斯指出我正确的方向！