可以通过schema().colDefs得到原表的字段定义：
pt = loadTable("dfs://GPS_data", "pt") shema = pt.schema().colDefs col1 = exec name from shema col2 = exec typeString from shema t = table(10:0, col1, col2)
或者直接通过一个不成立的where条件得到：
t=select * from pt where Send_time=1970.01.01T00:00:00.000