STARTSWITH 仅用于比较tuple1和tuple2，以检查tuple1是否包含tuple2。你不能把一个关系或一个包传给那个人。还有一点需要注意的是它只接受字符串（chararray）而不是整数。在groupby之前过滤从20040开始的系统\u period，并将系统\u period加载为chararray，然后根据需要在过滤器之后强制转换它。

transactions = LOAD '/home/cloudera/datasets/assignment2/Transactions.csv'
USING PigStorage(',') AS (Branch_Number:int, Contract_Number:int,
Customer_Number:int,Invoice_Date:chararray, Invoice_Number:int,
Product_Number:int, Sales_Amount:double, Employee_Number:int,
Service_Date:chararray, System_Period:chararray);
sysFilter = FILTER transactions BY STARTSWITH(System_Period, '20040');

其他之后
GROUP BY FLATTEN 结果，然后过滤

transactions = LOAD '/home/cloudera/datasets/assignment2/Transactions.csv'
USING PigStorage(',') AS (Branch_Number:int, Contract_Number:int,
Customer_Number:int,Invoice_Date:chararray, Invoice_Number:int,
Product_Number:int, Sales_Amount:double, Employee_Number:int,
Service_Date:chararray, System_Period:chararray);
sysGroup = GROUP transactions BY System_Period;
flatres = FOREACH sysGroup GENERATE group,FLATTEN(transactions);
sysFilter = FILTER flatres BY STARTSWITH(System_Period, '20040');