为什么查询被参数化后会中断?

问题描述 投票:2回答:1

我有2个表-SalesProductSales可以将产品存储为IdnName(旧式设计),并且Type列指定与之关联的实际typeProduct等是该表的子集表,该子表联接到此表以获取真实数据。 (在此示例中,Product是存储Idn的表以演示问题。)Sales |------------|--------------------|----------------| | Idn | Product Idn/Name | Type | |------------|--------------------|----------------| | 1 | 1 | Number | |------------|--------------------|----- ----------| | 2 | Colgate | Word | |------------|--------------------|----------------| Product (Idn) |------------|------------------| | Idn | Some Info | |------------|------------------| | 1 | ... | |------------|------------------|

通常,您不应该在Product Idn上加入这些表,因为它包含混合数据;但是,如果您选择LHS与RHS相匹配的行,则可以正常工作。例如,如果Product是存储

Idn

的表,则以下查询失败:SELECT * from sales JOIN product on sales.pid = product.idn
但是以下查询有效:

SELECT * from sales JOIN product on sales.pid = product.idn WHERE type = 'Number'

这也可以在Python 2 + SQLAlchemy + PyODBC中正常工作。但是,当我在Python 3 + SQLAlchemy + PyODBC中尝试此操作时,它给了我一个数据类型转换错误,并且仅在查询为[[parameterized
!]]时才会发生

现在,如果我在Python 2中将其设为u'number',它也会在此处中断;并且b'number'在Python 3中有效!我猜测Unicode转换存在一些问题。是否尝试guess编码并做错了什么?我可以更明确地解决此问题吗?

收到的错误是:Traceback (most recent call last): File "reproduce.py", line 59, in <module> print(cursor.execute(select_parametrized, ('number', 1)).fetchall()) pyodbc.ProgrammingError: ('42000', '[42000] [Microsoft][ODBC Driver 17 for SQL Server][SQL Server]Error converting data type varchar to numeric. (8114) (SQLFetch)

这里可能是问题所在,并且有没有解决convert之类的问题的好方法(因为它在以前的版本中有效)?

这里是可用于重现此问题而没有副作用(需要SQLAlchemyPyODBC)的查询:

import sqlalchemy import sqlalchemy.orm create_tables = """ CREATE TABLE products( idn NUMERIC(9) PRIMARY KEY ); CREATE TABLE sales( idn NUMERIC(9) PRIMARY KEY, pid VARCHAR(50) NOT NULL, type VARCHAR(10) NOT NULL ); """ check_tables_exist = """ SELECT * FROM products; SELECT * FROM sales; """ insert_values = """ INSERT INTO products (idn) values (1); INSERT INTO sales (idn, pid, type) values (1, 1, 'number'); INSERT INTO sales (idn, pid, type) values (2, 'Colgate', 'word'); """ select_adhoc = """ SELECT * FROM products JOIN sales ON products.idn = sales.pid AND sales.type = 'number' WHERE products.idn in (1); """ select_parametrized = """ SELECT * FROM products JOIN sales ON products.idn = sales.pid AND sales.type = ? WHERE products.idn in (?); """ delete_tables = """ DROP TABLE products; DROP TABLE sales; """ engine = sqlalchemy.create_engine('mssql+pyodbc://user:password@dsn') connection = engine.connect() cursor = engine.raw_connection().cursor() Session = sqlalchemy.orm.sessionmaker(bind=connection) session = Session() session.execute(create_tables) try: session.execute(check_tables_exist) session.execute(insert_values) session.commit() print(cursor.execute(select_adhoc).fetchall()) print(cursor.execute(select_parametrized, ('number', 1)).fetchall()) finally: session.execute(delete_tables) session.commit()

我有2张桌子-销售和产品。销售人员可以将产品存储为Idn或Name(旧式设计),并且Type列指定与之关联的实际类型。产品等是......>

sqlalchemy使用您的非参数化查询(select_adhoc)生成此SQL脚本
SELECT * FROM products JOIN sales ON products.idn = sales.pid AND sales.type = 'number' WHERE products.idn in (1);

但是使用参数化查询会生成此(select_parametrized)。 (我从SQL Server Profiler检查过)

declare @p1 int
set @p1=NULL
exec sp_prepexec @p1 output,N'@P1 nvarchar(12),@P2 int',N'
SELECT * FROM products
INNER JOIN sales ON products.idn = sales.pid 
    AND sales.type = @P1
WHERE products.idn in (@P2);
',N'number',1
select @p1

并且如果您在SQL Server上尝试此操作,则会得到此异常。

Msg 8114,第16级,状态5,第32行将数据类型varchar转换为数字时出错。

问题出在@ P1参数声明处。它将隐式转换为varchar(sales.type的类型),并导致此问题。可能使用Python 2会生成varchar。

并且如果您像这样更改查询,它将可以正常工作。或者,您需要将sales.type的类型更改为nvarchar。

select_parametrized = """ SELECT * FROM products INNER JOIN sales ON products.idn = sales.pid AND sales.type = CAST(? AS VARCHAR(50)) WHERE products.idn in (?); """

python sql sql-server
1个回答
0
投票
© www.soinside.com 2019 - 2024. All rights reserved.