Question

我正在使用SQL查询来查找所有具有特定RFID值的用户，每个用户可以具有多个RFID值。

我创建了一个准备好的语句，因为插入的值应该只是数字，所以实际上并不需要，但是，即使我仅输入一个存储的值，我仍然收到错误消息Incorrect number of arguments executing prepared statement在元组中。

可变RFID是函数中的参数

conn = Database.connect()  # returns an instance of connector.connect 

cursor = conn.cursor(prepared=True)  # Creates a cursor that is expecting 

sql_query = """SELECT RFID, users.UserID, FirstName, Surname, Email, Dob, Gender, Mobile 
               FROM users 
               JOIN RFIDs ON (users.UserID = RFIDs.UserID) 
               WHERE users.UserID = (SELECT UserID FROM RFIDs WHERE RFID = '%s');"""

cursor.execute(sql_query, (rfid,))  # Get user info


user_info_array = cursor.fetch()  # Store the results


conn.commit()  # Save the changes to the database

该查询在我使用时以及在其中手动输入值时均能正常工作。

预先感谢

Answer 1

您不应在％s左右使用单引号

sql_query = """SELECT RFID, users.UserID, FirstName, Surname, Email, Dob, Gender, Mobile 
           FROM users 
           JOIN RFIDs ON (users.UserID = RFIDs.UserID) 
           WHERE users.UserID = (SELECT UserID FROM RFIDs WHERE RFID = %s);"""

并且如spencer7593所建议的，对于子查询，应使用IN子句，而不是=（等于运算符），以避免子查询返回多于一行的错误

 sql_query = """SELECT RFID, users.UserID, FirstName, Surname, Email, Dob, Gender, Mobile 
       FROM users 
       JOIN RFIDs ON (users.UserID = RFIDs.UserID) 
       WHERE users.UserID IN (SELECT UserID FROM RFIDs WHERE RFID = %s);"""

或内部联接

sql_query = """SELECT RFID, users.UserID, FirstName, Surname, Email, Dob, Gender, Mobile 
   FROM users 
   JOIN RFIDs ON (users.UserID = RFIDs.UserID) 
   inner join  (
     SELECT UserID FROM RFIDs WHERE RFID = %s
   ) t on T.UserID  = users.UserID ;"""

准备的语句和不正确的参数数目

1 个答案: