there many ways to do what you requested.
The easiest is to use a subsearch:
index=index1 [ search index=index2 | rename asset_tag AS "Device ID" | fields "Device ID" ]
this solution has only one limit: if the subsearch has more than 50,000 results, the global result will be incomplete because there's a limit of 50,000 results in subsearches.
So if you could have more than 50,000 results in the secondary search, you have to use a different approach:
index=index1 OR index=index2
| rename asset_tag AS "Device ID"
| stats values(field1) AS field1 values(field2) AS field2 count BY "Device ID"
| where count >1
in this way you haven't any limit;
remember to put in the stats command al the fields (with values option) you want to display.
You could also use the join command but it isn't recommended because it's very slow and has the same limit of subsearch.