Merge Legend for graph from different SQL query

I have 2 sources of data for Graph
1 - Victoria metrics
sum(rate(requests[$interval])) by (source_id)
2 - PSQL DB source
SELECT concat('"', id::text,'"') as source_id, title as source_title FROM source

Right now I’m using Legend as {{source_id}} , but if there is any way to merge source_id from Victoria request with source_id from SELECT request and add have Legend as {{source_id}} - {{source_title}}