我正在尝试在 pig 的单个语句中对 2 个以上的关系执行左外连接。可能吗?
问候 哈里什
最佳答案
不幸的是,一步中的多路连接仅适用于内部连接。取自the official documentation :
Usage
...
Outer joins will only work for two-way joins; to perform a multi-way outer join, you will need to perform multiple two-way outer join statements.
因此,在他们添加可能性之前,这不会很快出现(没有开放的 JIRA 正在处理它),您将需要在 2 个语句中完成:
A = LOAD 'a' AS (a:chararray,b:int);
B = LOAD 'b' AS (a:chararray,b:chararray);
C = LOAD 'c' AS (a:chararray,b:chararray);
D = JOIN A by $0 LEFT OUTER, B BY $0;
E = JOIN D by $0 LEFT OUTER; C BY $0;
关于hadoop - 在 PIG 中一次左外连接超过 2 个关系,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/32186227/