如何在Pig Latin中使用WHERE子句编写左外连接？

Question

我与定义的模式有两个关系。我希望只找到关系中不存在的记录（参见this post左侧的中间可视化）。

我已经尝试了以下两种变体但没有成功，因为它们都返回下面的错误。如何在Pig中执行此类操作？

  

“ERROR 1200不匹配输入'在哪里'期待SEMI-COLON。”

join_result = JOIN relationA by (project_id, sequence_id) LEFT OUTER, relationB by (project_id, sequence_id) WHERE relationB (project_id, sequence_id)is null;

join_result = JOIN relationA by (project_id, sequence_id) LEFT OUTER, relationB by (project_id, sequence_id) WHERE (relationB.project_id is null) AND (relationB.sequence_id is null);

Answer 1

没有＆＃34; WHERE＆＃34; PIG中JOIN中的条款。您必须使用FILTER根据条件消除记录。

join_result = JOIN relationA by (project_id, sequence_id) LEFT OUTER, relationB by (project_id, sequence_id);
final_result = FILTER join_result BY (relationB.project_id is null AND relationB.sequence_id is null);