The Library · Insights
Deep dives across data, automation & AI
1262 in-depth articles — from Excel foundations to production machine learning. Filter by topic or difficulty to find exactly what you need.
SQLFoundation
Mastering SQL Joins with Aggregates: Combining GROUP BY, COUNT, and SUM Across Related Tables
Learn how to combine SQL joins with GROUP BY, COUNT, and SUM to answer real business questions across multiple related tables. This lesson covers fan-out pitfalls, LEFT JOIN behavior with HAVING, and how to structure complex queries with CTEs.
16 min read
Power AppsFoundation
Power Apps Form Modes Explained: Using NewForm, EditForm, and ViewForm to Control Data Entry Behavior
Learn how to control whether your Power Apps form creates new records, edits existing ones, or displays data as read-only — using NewForm(), EditForm(), and ViewForm(). This lesson walks you through a real employee directory app, wiring up buttons, handling submission outcomes, and building dynamic UI that responds to form state.
15 min read
Power BIFoundation
Implementing Power BI Gateway Clusters for High Availability and Load Balancing of Enterprise On-Premises Data Connections
Single gateways break under enterprise load — and when they do, every report that depends on on-premises data goes dark. Learn how to build Power BI gateway clusters that keep your data connections alive through failures, maintenance windows, and peak traffic surges.
20 min read
Power BIFoundation
DAX Implicit vs Explicit Measures: Why Auto-Generated Measures Fail in Complex Reports and How to Replace Them
Power BI's auto-generated measures feel convenient — until they silently produce wrong answers in filtered reports, ratio calculations, and time comparisons. Learn why implicit measures fail and how to replace every one with explicit DAX measures that scale to any complexity.
17 min read
Power BIFoundation
Understanding Power Query Data Types and Column Profiling: Preventing Errors Before They Reach Your Report
Data type mismatches and unexamined data quality issues are the number one source of silent errors in Power BI reports. This lesson teaches you how to use Power Query's type system and column profiling tools to catch every problem before it reaches your model.
17 min read
Power QueryFoundation
Implementing Custom Environment and Credential Management with M Language let Scoping: Structuring Query Context for Multi-Source, Multi-Tenant Data Pipelines
Hard-coded connection strings scattered across dozens of queries are a deployment disaster waiting to happen. This lesson shows you how to use M's let scoping and record-based context objects to build multi-environment, multi-tenant Power Query pipelines where a single configuration change propagates correctly to every downstream query.
16 min read
Power QueryFoundation
Connecting to and Extracting Data from REST APIs with Pagination in Power Query: Handling Next-Page Tokens, Offset Parameters, and Rate Limits
Most REST APIs return data in pages, not all at once — and if you don't know how to follow the pagination, you're only seeing a fraction of your data. This lesson teaches you how to write M code that loops through every page of an API response, handles cursor tokens and offset parameters, and respects rate limits so your queries don't get blocked.
17 min read
Microsoft ExcelFoundation
Writing VBA Procedures and Functions: Subs, Functions, and Scope Explained for Excel Automation
Master the essential building blocks of VBA: Sub procedures, Functions, parameters, and scope. Learn how to structure modular, reusable Excel automation that's easy to maintain and extend — with real-world examples throughout.
17 min read
Career DevelopmentExpert
Acquiring Freelance Data Clients Through Speaking and Teaching: How to Turn Conference Talks, Webinars, and Workshops into a Repeatable Pipeline of Inbound Inquiries
Most data freelancers overlook speaking and teaching as client acquisition tools — but a single well-designed talk can generate more qualified inbound inquiries than months of cold outreach. This lesson teaches you how to choose the right venues, design content that attracts buyers rather than peers, and build a follow-up system that converts attendees into paying clients.
34 min read
Career DevelopmentExpert
How to Navigate a Multi-Round Technical Interview Loop at a Data-Driven Company: Sequencing Your Preparation, Managing Fatigue, and Aligning Your Story Across Every Interviewer
Most candidates treat every round in a data interview loop as a separate event. That's the mistake that costs them offers. This lesson teaches you to treat the loop as a unified evaluation system — and prepare, perform, and follow up accordingly.
27 min read
Data EngineeringExpert
Building a Scalable Data Vault 2.0 Model in the Modern Data Stack: Hubs, Links, and Satellites with dbt and Snowflake
Data Vault 2.0 solves the messy reality of multi-source data integration without requiring you to redesign your warehouse every time a source system changes. This expert lesson walks you through building production-grade Hubs, Links, and Satellites using dbt incremental models and Snowflake, including hash key design, change detection, Point-In-Time tables, and performance optimization — with real SQL you can use today.
30 min read
Data EngineeringExpert
Pipeline Branching on Data Characteristics: Implementing Runtime Routing Logic to Split, Filter, and Redirect Records Based on Schema, Volume, and Quality Signals
Your pipeline treats all data the same — and that's exactly the problem. Learn how to build a composable runtime routing system that classifies records by schema version, volume tier, and quality score, then dispatches them to the right sink automatically. Real code, real trade-offs, production-ready patterns.
28 min read