I am running a simple select * with three UNIONS across 3 data extensions with only 8 fields each and it takes forever to run, like 5 minutes. Should I make three separate queries instead and run them concurrently? What gives with the UNION slowness?
DEs: 8 fields Number Text/128 Number Text/8 Text/50 EmailAddress EmailAddress Date
Column count: <100 in any one DE, <200 across all 3
What it's essentially doing is pulling the recipient lists of three different emails and adding them to a single daily log. This log gets referenced to determine which email should be sent.