在 sql 查询中多次使用相同的参数

Question

我正在使用 pyodbc 和 Microsoft SQL 服务器

我正在尝试在 python 中复制一个存储过程，其中针对每个 @currentSurveyId

执行此查询

SELECT *
                FROM
                (
                    SELECT
                        SurveyId,
                        QuestionId,
                        1 as InSurvey
                    FROM
                        SurveyStructure
                    WHERE
                        SurveyId = @currentSurveyId
                    UNION
                    SELECT 
                        @currentSurveyId as SurveyId,
                        Q.QuestionId,
                        0 as InSurvey
                    FROM
                        Question as Q
                    WHERE NOT EXISTS
                    (
                        SELECT *
                        FROM SurveyStructure as S
                        WHERE S.SurveyId = @currentSurveyId AND S.QuestionId = Q.QuestionId
                    )
                ) as t
                ORDER BY QuestionId

在 Python 中，我目前有：

cursor.execute("""SELECT UserId FROM dbo.[User]""")
allSurveyID = cursor.fetchall()

for i in allSurveyID:
    p = i
    test = cursor.execute("""SELECT *
                FROM
                (
                    SELECT
                        SurveyId,
                        QuestionId,
                        1 as InSurvey
                    FROM
                        SurveyStructure
                    WHERE
                        SurveyId = (?)
                    UNION
                    SELECT 
                        (?) as SurveyId,
                        Q.QuestionId,
                        0 as InSurvey
                    FROM
                        Question as Q
                    WHERE NOT EXISTS
                    (
                        SELECT *
                        FROM SurveyStructure as S
                        WHERE S.SurveyId = (?)AND S.QuestionId = Q.QuestionId
                    )
                ) as t
                ORDER BY QuestionId""",p)

for i in test:
    print(i)

该参数只用一次（如果我从 UNION 开始删除所有内容）。当尝试在查询的其余部分使用相同的参数时，出现以下错误：('The SQL contains 3 parameter markers, but 1 parameters were supplied', 'HY000')

是否可以在同一个查询中多次使用同一个参数？

谢谢

Answer 1

pyodbc 本身仅支持“qmark”（位置）参数（参考：here），但对于 T-SQL（Microsoft SQL 服务器）我们可以使用 匿名代码块以避免多次传递相同的参数值：

cnxn = pyodbc.connect(connection_string)
crsr = cnxn.cursor()

sql = """\
SET NOCOUNT ON;
DECLARE @my_param int = ?;
SELECT @my_param AS original, @my_param * 2 AS doubled;
"""
results = crsr.execute(sql, 2).fetchone()
print(results)  # (2, 4)

Answer 2

如果重复使用相同的参数值，只需乘以 one-item 参数列表：

cursor.execute(sql, [p]*3)

还考虑为需要两个 qmark 的 LEFT JOIN（或 FULL JOIN）重构您的 SQL：

SELECT DISTINCT
       ISNULL(S.SurveyId, ?) AS SurveyId, 
       Q.QuestionId, 
       IIF(S.SurveyId IS NOT NULL, 1, 0) AS InSurvey 
FROM Question Q
LEFT JOIN SurveyStructure S
  ON S.QuestionId = Q.QuestionId 
  AND S.SurveyId = ?
ORDER BY Q.QuestionId

甚至可能只有一个参数：

SELECT MAX(S.SurveyId) AS SurveyId, 
       Q.QuestionId, 
       IIF(S.SurveyId IS NOT NULL, 1, 0) AS InSurvey 
FROM Question Q
LEFT JOIN SurveyStructure S
  ON S.QuestionId = Q.QuestionId 
  AND S.SurveyId = ?
GROUP BY Q.QuestionId, 
         IIF(S.SurveyId IS NOT NULL, 1, 0)
ORDER BY Q.QuestionId

在 sql 查询中多次使用相同的参数

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pyodbc