如何使用Python / SQLAlchemy和MSSQL在一个SQL中执行多个插入/更新查询？

Question

I'm new to python and SQLAlchemy, I'm trying to understand how to execute multiple insert/update queries in one SQL using Python/SQLAlchemy:

Requirement Execute multiple insert/update in one SQL:

DECLARE @age INT = 160
INSERT INTO TEST_TABLE VALUES ('QZ_TEST', @age + 1)
INSERT INTO TEST_TABLE VALUES ('QZ_TEST', 'not a number')
INSERT INTO ANOTHER_TABLE VALUES ('QZ_TEST', @age + 2)

Understand that this query looks ugly, but we do have many similar queries. (we're using a legacy database which is around 20 years old)

Python Code

def OdbcEngineSA(driver, conn_str):
    def connect():
        return pyodbc.connect(conn_str, autocommit=True, timeout=120)
    return sqlalchemy.create_engine(driver + '://', creator=connect)

def get_db_connection():
    return OdbcEngineSA('mssql', 'DSN=mssql;Server=server,15001;database=DEV;UID=user_abc;PWD=pw_')

def main():
    db_connection = get_db_connection()
    sql = """
    DECLARE @age INT = 160
    INSERT INTO TEST_TABLE VALUES ('QZ_TEST', @age + 1)
    INSERT INTO TEST_TABLE VALUES ('QZ_TEST', 'not a number')
    INSERT INTO ANOTHER_TABLE VALUES ('QZ_TEST', @age + 2)
    """
    try:
        db_connection.execute(sql)
        db_connection.commit()
        logger.info('db updated')   
    except Exception as e:
        logger.error('Exception captured as expected: %s', e)
        db_connection.rollback()

Please note that

INSERT INTO TEST_TABLE VALUES ('QZ_TEST', 'not a number')

will trigger an Error if I ran this single query with my SQL client: [S0001][245] Conversion failed when converting the varchar value 'not a number' to data type int.

I'm expecting an exception captured by Python, however, the Python code runs without any exception. There's no exception captured by Python even though I replaced the SQL with :

BEGIN TRY
        DECLARE @age INT = 160
        INSERT INTO TEST_TABLE VALUES ('QZ_TEST', @age + 1)
        INSERT INTO TEST_TABLE VALUES ('QZ_TEST', 'not a number')
        INSERT INTO ANOTHER_TABLE VALUES ('QZ_TEST', @age + 2)
END TRY
    BEGIN CATCH
        DECLARE @ErrorMessage NVARCHAR(4000)
        DECLARE @ErrorSeverity INT
        DECLARE @ErrorState INT

        SELECT 
            @ErrorMessage = ERROR_MESSAGE(),
            @ErrorSeverity = ERROR_SEVERITY(),
            @ErrorState = ERROR_STATE()

        RAISERROR (@ErrorMessage,
                   @ErrorSeverity, -- Level 16
                   @ErrorState
                   )
    END CATCH

My Questions

• Am I using the correct method to execute the Query?
• If my code was fine, how can I capture the actual SQL exception from Python?

Answer 1

The execute command may be having issues preparing your statement, since it is in fact, multiple statements. For what you're trying to do, I believe you may want to take a look at executemany :

https://github.com/mkleehammer/pyodbc/wiki/Cursor#executemanysql-paras

It takes a different form and binds your INSERT values as tuples within a list.

Good luck!