1. Introduction to Power Query
As an ETL layer, Power Query organizes how data is acquired, shaped, and prepared for reporting. The training starts with its role in Excel and Power BI, the query editor interface, Applied Steps and preview mechanisms, and the principles of designing queries for later analytical use.
- the role of Power Query in the data preparation process (ETL),
- Power Query in Excel vs Power BI – scope of capabilities,
- interface: query editor, Applied Steps, data preview,
- principles of designing queries for subsequent reporting.
2. Data sources and import
Power Query connects to files, folders, databases, and online sources, but each source type brings different import considerations. This section addresses loading Excel, CSV, TXT, JSON, and XML data, consolidating files from folders, and managing connection settings, credentials, and privacy levels.
- import from files: Excel, CSV, TXT, JSON, XML,
- import from a folder – consolidation of multiple files,
- connections to databases and online sources,
- connection settings, credentials, data privacy.
3. Data cleaning and preparation
Raw datasets often contain technical rows, inconsistent headers, empty records, and mixed data types that block further analysis. Here the focus is on removing unnecessary rows and columns, standardizing dates, numbers, and text, and cleaning duplicates, blanks, names, and dictionary values.
- removing unnecessary columns and rows,
- working with headers, technical rows, footers,
- standardizing data types (dates, numbers, text),
- removing duplicates and empty values,
- standardization of column names and dictionary values.
4. Data transformations
Column-level operations form the basis of most analytical preparation work in Power Query. Participants practice splitting and merging fields, extracting text, pivoting and unpivoting structures, grouping and aggregating data, and using filters, calculated columns, logical rules, and value mapping.
- operations on columns: splitting, merging, extracting text fragments,
- changing the data format: pivot and unpivot,
- grouping and aggregations (Group By),
- filtering, sorting, creating calculated columns,
- logical conditions and data transformation rules,
- replacing values and mapping categories.
5. Merging and appending data
When data comes from multiple tables, the result depends on both the join logic and the source structure. The section covers Merge with left, right, inner, and full joins, Append for combining datasets, and ways to address missing matches or conflicting values before consolidation.
- Merge – merging tables (joins: left, right, inner, full),
- Append – appending data (union) from multiple sources,
- handling missing matches and data conflicts,
- preparing data structures for correct merging.
6. Automation and scalability of solutions
Building queries for repeated use requires more than a one-time refresh. This part focuses on manual and automatic updates, parameterized queries such as date ranges or file paths, and working with dynamic folders and changing file structures in cyclical reporting processes.
- data refresh – manual and automatic,
- working with dynamic folders and changing file structure,
- query parameters (e.g. date range, file location),
- preparing queries for cyclical reporting.
7. Performance and stability of queries
Slow refreshes usually result from step order, excessive source volumes, or poorly designed query flow. Participants work on limiting data as early as possible, diagnosing bottlenecks, and handling the most common refresh issues that affect stability in everyday reporting.
- the order of steps and refresh time,
- limiting data volumes already at the import stage,
- diagnostics of slow queries,
- the most common problems during data refresh.
8. The M Language in Power Query – practical context
M language is presented as the logic behind query steps rather than a separate programming topic. The section explains let/in syntax, step naming, and code readability, then shows where generated M appears in Power Query and how to edit it safely for uncommon transformations.
- M language syntax: let/in, steps, code readability,
- where M code appears in Power Query and how to modify it consciously,
- simple examples of editing M for unusual transformations.