Question: I have a scenario like below:

Collection A has:

```
<field name="id" type="string" indexed="true" stored="true"/> <!--  Not unique in Collection A but unique in Collection B as uid-->
<field name="type" type="string" indexed="true" stored="true"/>

```

Collection B has:

```
<field name="uid" type="string" indexed="true" stored="true"/> <!-- unique -->
<field name="name" type="string" indexed="true" stored="true"/ 

```

Now I need to join this two collection like :

For all type='xxx' from Collection A, get me all data from Collection B.

Am new to solr, not even sure its possible or not. But this can be easily done in DB. Any suggestion?

Answer: 
The above solution only works when both the collections are in the same server. If they reside in different servers, then solr cloud has limitations to it.
[How to join two different cores from two different Solr servers?](https://stackoverflow.com/questions/44386132/how-to-join-two-different-cores-from-two-different-solr-servers)
Something like this should help you...

> 
> {!join from=fromField to=toField fromIndex=fromCoreName}fromQuery
> 
> 
>