No such table error when using DataFrame created with pd. read_sas

I currently try to merge two DataFrames by using pandasql, but I don't know how to create a new column for my DataFrame. I tried the code "ALTER TABLE crsp ADD monthid INT()", and it told me that there is no such table: crsp. But I have created a crsp DataFrame by using pd.read_sas, so I'm not sure how to solve this error.

Does someone know how to solve this problem?

import pandas as pd
from pandasql import sqldf
mysql = lambda q: sqldf(q, globals())
crsp = pd.read_sas("crsp_nasdaq100.sas7bdat", encoding= "ISO-8859-1 ")
query = "ALTER TABLE crsp \
         ADD monthid INT()"
mysql(query)

Error message:
OperationalError                          Traceback (most recent call last)
~/opt/anaconda3/lib/python3.9/site-packages/sqlalchemy/engine/base.py in _execute_context(self, dialect, constructor, statement, parameters, execution_options, *args, **kw)
   1770                 if not evt_handled:
-> 1771                     self.dialect.do_execute(
   1772                         cursor, statement, parameters, context

~/opt/anaconda3/lib/python3.9/site-packages/sqlalchemy/engine/default.py in do_execute(self, cursor, statement, parameters, context)
    716     def do_execute(self, cursor, statement, parameters, context=None):
--> 717         cursor.execute(statement, parameters)
    718 

OperationalError: no such table: crsp

The above exception was the direct cause of the following exception:

OperationalError                          Traceback (most recent call last)
~/opt/anaconda3/lib/python3.9/site-packages/pandasql/sqldf.py in __call__(self, query, env)
     60             try:
---> 61                 result = read_sql(query, conn)
     62             except DatabaseError as ex:

~/opt/anaconda3/lib/python3.9/site-packages/pandas/io/sql.py in read_sql(sql, con, index_col, coerce_float, params, parse_dates, columns, chunksize)
    627     else:
--> 628         return pandas_sql.read_query(
    629             sql,

~/opt/anaconda3/lib/python3.9/site-packages/pandas/io/sql.py in read_query(self, sql, index_col, coerce_float, parse_dates, params, chunksize, dtype)
   1578 
-> 1579         result = self.execute(*args)
   1580         columns = result.keys()

~/opt/anaconda3/lib/python3.9/site-packages/pandas/io/sql.py in execute(self, *args, **kwargs)
   1423         """Simple passthrough to SQLAlchemy connectable"""
-> 1424         return self.connectable.execution_options().execute(*args, **kwargs)
   1425 

~/opt/anaconda3/lib/python3.9/site-packages/sqlalchemy/engine/base.py in execute(self, statement, *multiparams, **params)
   1247 
-> 1248             return self._exec_driver_sql(
   1249                 statement,

~/opt/anaconda3/lib/python3.9/site-packages/sqlalchemy/engine/base.py in _exec_driver_sql(self, statement, multiparams, params, execution_options, future)
   1546         dialect = self.dialect
-> 1547         ret = self._execute_context(
   1548             dialect,

~/opt/anaconda3/lib/python3.9/site-packages/sqlalchemy/engine/base.py in _execute_context(self, dialect, constructor, statement, parameters, execution_options, *args, **kw)
   1813         except BaseException as e:
-> 1814             self._handle_dbapi_exception(
   1815                 e, statement, parameters, cursor, context

~/opt/anaconda3/lib/python3.9/site-packages/sqlalchemy/engine/base.py in _handle_dbapi_exception(self, e, statement, parameters, cursor, context)
   1994             elif should_wrap:
-> 1995                 util.raise_(
   1996                     sqlalchemy_exception, with_traceback=exc_info[2], from_=e

~/opt/anaconda3/lib/python3.9/site-packages/sqlalchemy/util/compat.py in raise_(***failed resolving arguments***)
    206         try:
--> 207             raise exception
    208         finally:

~/opt/anaconda3/lib/python3.9/site-packages/sqlalchemy/engine/base.py in _execute_context(self, dialect, constructor, statement, parameters, execution_options, *args, **kw)
   1770                 if not evt_handled:
-> 1771                     self.dialect.do_execute(
   1772                         cursor, statement, parameters, context

~/opt/anaconda3/lib/python3.9/site-packages/sqlalchemy/engine/default.py in do_execute(self, cursor, statement, parameters, context)
    716     def do_execute(self, cursor, statement, parameters, context=None):
--> 717         cursor.execute(statement, parameters)
    718 

OperationalError: (sqlite3.OperationalError) no such table: crsp
[SQL: ALTER TABLE crsp          ADD monthid INT()]
(Background on this error at: https://sqlalche.me/e/14/e3q8)

During handling of the above exception, another exception occurred:

PandaSQLException                         Traceback (most recent call last)
/var/folders/jr/xg1lg5x50w18f16_0bh805l80000gn/T/ipykernel_933/1396149349.py in <module>
      1 query = "ALTER TABLE crsp \
      2          ADD monthid INT()"
----> 3 mysql(query)

/var/folders/jr/xg1lg5x50w18f16_0bh805l80000gn/T/ipykernel_933/285284892.py in <lambda>(q)
----> 1 mysql = lambda q: sqldf(q, locals())

~/opt/anaconda3/lib/python3.9/site-packages/pandasql/sqldf.py in sqldf(query, env, db_uri)
    154     >>> sqldf("select avg(x) from df;", locals())
    155     """
--> 156     return PandaSQL(db_uri)(query, env)

~/opt/anaconda3/lib/python3.9/site-packages/pandasql/sqldf.py in __call__(self, query, env)
     61                 result = read_sql(query, conn)
     62             except DatabaseError as ex:
---> 63                 raise PandaSQLException(ex)
     64             except ResourceClosedError:
     65                 # query returns nothing

PandaSQLException: (sqlite3.OperationalError) no such table: crsp
[SQL: ALTER TABLE crsp          ADD monthid INT()]
(Background on this error at: https://sqlalche.me/e/14/e3q8)