Power BI — Fundamentals
What is Power BI
Power BI is Microsoft's business intelligence platform for creating interactive reports and dashboards. It connects to hundreds of data sources, transforms data with Power Query, creates relationships, and builds visualizations.
Key Components
Power BI Desktop → Free desktop app for report creation
Power BI Service → Cloud platform for sharing and collaboration
Power BI Mobile → iOS/Android for consuming reports
Power BI Gateway → Connect cloud to on-premise data
Report structure:
Dataset = data source + transformations + relationships
Report = collection of visualizations on one or more pages
Dashboard = pinned tiles from multiple reports (Service only)
Connecting Data Sources
Direct query sources:
Azure SQL, SQL Server, PostgreSQL, MySQL
Salesforce, SharePoint, Google Analytics
REST APIs, web scraping
File sources:
Excel (.xlsx), CSV, JSON, XML
PDF (extract tables)
Power BI Desktop files (.pbix)
Azure Blob Storage / Data Lake
Import vs DirectQuery:
Import: Data loaded into Power BI (fast, full features)
DirectQuery: Queries run live against source (always current, slower)
Use Import when: data fits in memory, performance matters
Use DirectQuery when: data is huge or must be real-time
Power Query Basics (M language)
powerquery
// Load and transform in Power Query Editor
let
// Step 1: Connect to source
Source = Excel.Workbook(File.Contents("C:\sales.xlsx"), null, true),
Sheet1 = Source{[Item="Sheet1",Kind="Sheet"]}[Data],
// Step 2: Promote headers
PromotedHeaders = Table.PromoteHeaders(Sheet1),
// Step 3: Clean data
RemovedBlanks = Table.SelectRows(PromotedHeaders,
each [CustomerName] <> null and [CustomerName] <> ""),
// Step 4: Add calculated column
AddedRevenue = Table.AddColumn(RemovedBlanks, "Revenue",
each [Quantity] * [UnitPrice], type number),
// Step 5: Filter
FilteredDates = Table.SelectRows(AddedRevenue,
each [OrderDate] >= #date(2024, 1, 1))
in
FilteredDates
