In metabase I have created 2 Questions how to do union all on those 2 questions? i cannot perform that neither from editor nor from SQL query. If you guys could help me?
You can perform UNION normally if related tables are in the same DB. Try this in the Sample database:
select TOP 5 Email from PEOPLE
union
select TOP 5 Email from ACCOUNTS
But as I know, in Metabase you cannot do UNION between different DBs.