我正在使用 SQL 查询查找具有特定 RFID 值的所有用户,每个用户可以有多个 RFID 值。
我已经创建了一个准备好的语句,这并不是真正需要的,因为插入的值应该只是数字,但是,我不断收到错误消息说 Incorrect number of arguments executing prepared statement
即使我只输入一个存储在元组中的值。
变量RFID是函数内的一个参数
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
查询工作正常,因为我已经使用过它,并且在手动输入值时。
提前致谢
最佳答案
你不应该在 %s 周围使用单引号
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);"""
并且正如 spencer7593 所建议的那样,子查询应该使用 IN 子句而不是 =(等于运算符)这是为了避免子查询返回多于一行时的错误
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);"""
或内部连接
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 ;"""
关于python - 准备好的语句和不正确的参数数量,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/56797462/