在 tsql 和 pyodbc 中参数化 TOP 值

Question

我尝试参数化从表中获取的顶行数。

我试过了

db.cursor.execute(
        '''
        SELECT TOP ? VALUE FROM mytable 
        WHERE param = ? 
        ''',
        top_value, param
    )

它显示

pyodbc.ProgrammingError: ('42000', "[42000] [Microsoft][ODBC Driver 17 for SQL Server][SQL Server]'@P1' 附近的语法不正确。(102) (SQLExecDirectW)")

像下面这样的字符串插值可以工作。

    db.cursor.execute(
        f'''
        SELECT TOP {top_limit} VALUE FROM mytable 
        WHERE SITE_SK_FK = ? 
        ''',
        param
    )

我需要将它作为参数传递，还是字符串插值就足够了？

Answer 1

您可以top通过用括号将值括起来来参数化：

DECLARE @Top int = 5;

With Tally(N) AS
(
    SELECT ROW_NUMBER() OVER(ORDER BY @@SPID)
    FROM sys.objects
)

-- This works just fine
SELECT TOP (@Top) N
FROM Tally;

-- This will raise an error: Incorrect syntax near '@Top'
SELECT TOP @Top N 
FROM Tally;

应用于您发布的代码：

SELECT TOP (?) VALUE 
FROM mytable 
WHERE param = ?