Day 1: Power BI Basics & Interface

Power BI is Microsoft's business intelligence and data visualisation platform. It has three main components: Power BI Desktop (free Windows application for building reports), Power BI Service (cloud-based web app at app.powerbi.com for sharing and collaboration), and Power BI Mobile (iOS/Android app for viewing reports). For data analyst roles in India, Power BI Desktop is the primary tool — most interview questions and practical tests are based on Desktop.

Report View: where you build visuals — drag fields, format charts, and create the final dashboard layout. Data View: shows your data in a tabular format, like an Excel sheet — useful for checking data after transformations and verifying calculated columns. Model View: shows the relationships between tables as a diagram — where you create, edit, and review table relationships. Switch between views using the icons on the left sidebar.

Power BI Desktop is a free Windows application installed on your computer — used to build, design, and model reports. It works offline and has the full feature set for development. Power BI Service is the cloud platform (app.powerbi.com) — used to publish, share, schedule data refresh, and collaborate. You publish a .pbix file from Desktop to Service to make it accessible to others. Service has some features Desktop does not: scheduled refresh, dashboards (as opposed to reports), row-level security administration, and sharing with non-Desktop users.

.pbix is the standard Power BI Desktop file format — it contains everything: data model, queries, relationships, measures, and report visuals. .pbit is a Power BI template file — it contains the structure (data model, queries, report layout) but not the data, useful for creating reusable report templates. When publishing to Power BI Service, you upload the .pbix file. The Service stores it as a dataset (data model) and report (visuals) separately.

Import Mode: data is copied into Power BI's in-memory engine (VertiPaq). Fast performance, works offline, but data is only as fresh as the last refresh. Most common mode for datasets under 1 GB. DirectQuery: Power BI sends queries directly to the source database every time a visual is interacted with. Data is always current but performance depends on the source database. Live Connection: connects to an existing Analysis Services model or Power BI dataset without importing — the model is maintained externally. Composite Model: combines Import and DirectQuery in the same model (advanced).