cx_oracle 缺少右括号

Question

我正在使用 cx_oracle python 库来查找在过去 90 分钟内具有 modifiedDate 的任何记录。import cx_Oracleimport datetimefrom datetime import timedeltaimport config as configtimeNow = datetime.datetime.now()previousTime = timeNow - datetime.timedelta (minutes = 0)connection = cx_Oracle.connect(user, password, connection)cur = connection.cursor()statement = "SELECT * FROM woodburn_all WHERE modifiedDate >= to_date(" + str(previousTime) +")"print statementr = cur.execute(statement)for row in cur:    print row打印的 select 语句看起来正确：SELECT * FROM woodburn_all WHERE to_date(modifiedDate) >= to_date(2018-09-2 11:02:10.460000)我没有看到我错过了什么括号。这是一些奇怪的日期/时间吗？