Table Joins
from different sources in Power Automate

Why this pattern

Power Automate doesn't have a native JOIN operator across data sources. The recommended approach is to retrieve each dataset, build a lookup map and iterate to enrich the primary list. This page documents a clean, reusable version of that pattern.

Steps

1. Retrieve list A from source 1 (e.g., SharePoint list).
2. Retrieve list B from source 2 (e.g., Excel table or SQL).
3. Build lookup: use Select + Compose to project list B into a key → value object.
4. Join: iterate over list A, look up matching keys in B's object and produce the enriched record.
5. Write output to the destination (Excel, Dataverse, email, etc.).

Performance tips

• Avoid nested Apply to each — it scales O(n·m). Use a Compose-based lookup instead (O(n)).
• Trim list A and B server-side with OData filters before bringing data into the flow.
• Cache the lookup object in a variable to avoid re-evaluation in each iteration.