Power BI Data Analyst (PL-300) Study Notes

Prepare the Data with Power Query

Connect, profile, clean, and load data sources

Domain Weight

Prepare the data accounts for 27% of the PL-300 exam.

Data preparation is 27% of PL-300. You must know Power Query transformations, connection modes, and when to push vs import data.

Connection Mode	Data Location	Best For
Import	Copied into model memory	Smaller datasets, full DAX flexibility, offline reports
DirectQuery	Stays in source database	Large datasets, real-time needs; limited DAX
DirectLake	Parquet in OneLake, no import	Fabric lakehouse; fast large-model analytics
Live Connection	Connects to existing dataset	Reuse enterprise semantic model

Power Query Essentials

Get Data — connectors for SQL, Excel, SharePoint, web APIs, folders
Query folding — push transformations to source for performance (watch for breaking steps)
Common transforms — remove columns, filter rows, split/merge columns, unpivot, group by
Data profiling — column quality, distribution, value counts in Power Query Editor
Parameters — dynamic sources, environment switching, reusable queries
M language — advanced custom columns and functions when GUI is insufficient

Query Folding

Steps that break folding (certain custom columns, complex M) force full data pull before transform — hurts DirectQuery and large imports.

Exam Focus Areas

Import for self-contained models; DirectQuery when data is too large or must be live
Unpivot wide tables to tall format for time-series analysis
Use parameters for dev/test/prod connection strings

Practice This Domain

Test your understanding with free practice questions at /certifications/microsoft/pl-300/practice — focus on: Connect to data sources, Data profiling and cleaning, Power Query transformations.

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