Power Fx function

LookUp — Power Fx function reference

Return the first matching record.

Syntax

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LookUp( Source, Condition [, Result ] )

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LookUp(Staff, ID = locId)

→ One record

The optional third argument projects a single column instead of returning the whole record.

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LookUp(Products, SKU = txtSKU.Text, Price)

→ Just the Price field (a number), not the whole record

Field access on a missing record returns blank rather than erroring, so wrap it for a friendly fallback.

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IfError(LookUp(Accounts, AccountNumber = txtAcct.Text).Name, "Not found")

→ "Not found" if no account matches

LookUp returns only the first matching record. If more than one row matches, which row you get is whatever order the data source happens to return — sort first with LookUp(Sort(Source, ...), Condition) if you need a specific one.
A LookUp with no match returns blank, not an error. Chaining a field straight onto it (LookUp(...).Name) also returns blank rather than failing, which can hide a missing-record bug until it reaches production.
The condition needs to be delegable for the connector (simple column comparisons on SharePoint/Dataverse/SQL). A non-delegable condition silently searches only the first 500–2000 rows instead of the whole table.

From Filtering, search & sort