我使用下面的pig脚本来计算一个运行总数（pig本地模式）

Register /home/ec2-user/pig*/bin/piggybank-0.12.0.jar ;   
 define Sum org.apache.pig.piggybank.evaluation.int.Sum();
 define Over org.apache.pig.piggybank.evaluation.Over();
 define Stitch org.apache.pig.piggybank.evaluation.Stitch();
 A = load '/home/ec2-user/staff_data.csv' using PigStorage(',') as (id:int, name:chararray, salary:int, department:chararray);
 B = group A by department;
 C = foreach B {
     C1 = order A by salary;
     generate flatten(Stitch(C1, Over(C1.department, 'Sum(C1.salary)')));
 };

但是，我得到以下错误
未知总额（c1.工资）
有什么想法吗？
编辑：
我自己想出了答案。在这里：

Register /home/ec2-user/pig*/bin/piggybank-0.12.0.jar ;   
 define Over org.apache.pig.piggybank.evaluation.Over();
 define Stitch org.apache.pig.piggybank.evaluation.Stitch();
 A = load '/home/ec2-user/staff_data.csv' using PigStorage(',') as (id:int, name:chararray, salary:int, department:chararray);
 B = group A by department;
 C = foreach B {
     C1 = order A by salary;
     generate flatten(Stitch(C1, Over(C1.salary, 'sum(int)')));
 };