Merging two feeds to one stream. How unite?

Question

I work with Yahoo Pipes, and have two 'XPath Fetch Page' sources. Individually, they work perfectly.

One Page. Creating pubDate field

Second Page. Creating other fields

At now, i want insert pubDate filed from first feed to second. I will use UNION module

But pubDate field is not present in the final result. If i change input order of Union module i get pubDate only. Why? How insert pubDate in the output stream?

Answer 1

Unfortunately, you cannot easily merge or join entries of two different feeds.

The union operator works like in SQL: the union of a feed with entries { entryA, entryB, entryC } and another feed with entries { entryX, entryY } becomes the set { entryA, entryB, entryC, entryX, entryY }. That is, the entries are unmodified. The entries from both feeds are included in the resulting set without any modification or interaction between the two feeds.

The only way to merge data from two different sources is by nesting your pipes:

1. Create a first pipe that takes parameter X
2. Create a second pipe that will have a loop, and for each entry it will make a call to the first pipe, passing some value as parameter X

It's not efficient, not great, but possible, it works.