When working with multiple datasets in Power Query, you often need to stack data from different tables or sources. Appending queries is a powerful feature that allows you to combine data efficiently for analysis in Power BI or Excel.

In this guide, we’ll cover what query appending is, how to append queries step by step, and best practices to ensure accurate and optimized data merging.

1. What is Query Appending in Power Query?

Appending queries in Power Query means stacking data from multiple tables into a single dataset with matching columns. This is useful when you:

✅ Have multiple datasets with the same structure (e.g., monthly sales reports).
✅ Need to combine data from multiple sources (e.g., different regions or departments).
✅ Want to consolidate historical and new data into a single table.

Power Query provides two types of appends:

✔ Append Queries – Combines multiple tables into one new table.
✔ Append Queries as New – Creates a new query without modifying existing ones.

2. How to Append Queries in Power Query (Step-by-Step Guide)

Follow these steps to append queries in Power Query:

Step 1: Load Data into Power Query

  1. Open Power BI or Excel and go to the Power Query Editor.
  2. Load the datasets you want to append by selecting Home > Get Data.
  3. Ensure that all tables have the same column names and data types.

Step 2: Append Queries

  1. In the Power Query Editor, go to the Home tab.
  2. Click Append Queries (or Append Queries as New if you want a new table).
  3. Select the tables you want to append.
  4. Click OK to merge them.

Step 3: Verify and Clean the Data

  1. Check if all rows are stacked correctly.
  2. Ensure there are no duplicate columns or data type mismatches.
  3. Rename columns if necessary.
  4. Click Close & Load to apply changes to Power BI or Excel.

3. Best Practices for Appending Queries

✔ Ensure Column Consistency: All tables must have identical column names and data types to prevent errors.
✔ Handle Missing Columns: If one table lacks a column, Power Query will insert null values. Consider adding missing columns before appending.
✔ Optimize Performance: If dealing with large datasets, disable unnecessary query steps to improve performance.
✔ Use Append Queries as New for Safety: Keep original queries intact by appending as a new query.

4. Common Issues and How to Fix Them

Issue 1: Data Types Don’t Match

Fix: Before appending, go to Transform > Data Type and ensure all columns have consistent data types.

Issue 2: Extra or Missing Columns

Fix: Ensure that all queries have matching column structures. Use Table.ReorderColumns() in M Language if needed.

Issue 3: Performance Issues with Large Data

Fix: Load only necessary data, disable unnecessary query steps, and use DirectQuery mode if applicable.

Conclusion

✅ Appending queries is a crucial technique in Power Query for combining data efficiently.
✅ Follow best practices to ensure clean and structured data.
✅ Troubleshoot common issues to optimize performance and accuracy.

By mastering query appending, you can streamline your data transformation process and build better Power BI reports!