Power BI Lesson 8 – Data Source Settings | Dataplexa

Power BI Course

I. Beginner Level
1. Introduction to Power BI 2. Business Intelligence Basics 3. Power BI Components 4. Installing Power BI Desktop 5. Power BI Interface 6. Getting Data from Files 7. Getting Data from Databases 8. Data Source Settings 9. Data Types 10. Basic Transformations 11. Model View Basics 12. Report View Basics 13. Page Navigation 14. Visualization Basics 15. Basic Charts
II. Power Query
16. Introduction to Power Query 17. Query Editor Layout 18. Applied Steps 19. Transform Rows & Columns 20. Grouping Data 21. Split & Merge Columns 22. Append & Merge Queries 23. Advanced Data Cleaning 24. Replace Errors 25. Data Formatting 26. Custom Columns 27. Conditional Columns 28. Date & Time Transforms 29. Parameters 30. Introduction to M Language
III. DAX
31. Introduction to DAX 32. DAX Syntax 33. Measures vs Columns 34. Common DAX Functions 35. Row & Filter Context 36. CALCULATE Function 37. Time Intelligence 38. Iterator Functions 39. Advanced DAX 40. DAX Best Practices
IV. Visualization & Service
41. Visualization Types 42. Visual Formatting 43. Slicers & Filters 44. Custom Tooltips 45. Bookmarks 46. Power BI Service 47. Workspaces 48. Sharing Reports 49. Refresh Schedules 50. Power BI Admin
Beginner Level · Lesson 8

Data Source Settings

Every connection you create in Power BI is stored somewhere — and Data Source Settings is the single control panel where you can see, edit, update, and fix all of them without opening every query one by one. Knowing this screen well will save you every time a file moves, a password changes, or a refresh mysteriously breaks.

What Data Source Settings Actually Is

When you connect to any source — a file, a database, a web URL — Power BI stores two things: the connection details (path, server address, query) and the credentials (username, password, Windows auth). Data Source Settings is where both live. You reach it from the ribbon at Home → Transform Data → Data Source Settings.

Data Source Settings
Data sources in current file
Global permissions
📗
C:\Reports\SalesData.xlsx
Excel Workbook · Anonymous
Connected
🗄️
SQLSRV01\PRODUCTION · SalesDB
SQL Server · Windows authentication
Connected
📄
C:\Downloads\temp_export.csv
CSV · Anonymous
File not found
Edit Permissions
Change Source
Clear Permissions
Close

Current File vs Global Permissions

The Data Source Settings dialog has two tabs and the difference between them trips up a lot of beginners. Getting this wrong means you think you fixed a connection but you actually fixed it in the wrong place.

Data sources in current file
Shows only the data sources used by the report you currently have open. If you change a file path or credential here, it only affects this report file.
Use this tab for: fixing a broken path in the report you are working on right now
Global permissions
Shows every data source you have ever connected to across all .pbix files on your machine. Credentials stored here are shared — any report using the same source will use the same stored credential.
Use this tab for: updating a database password that is used by multiple reports

Changing a Source Path

The most common task in Data Source Settings is updating a file path after a source file has moved or been renamed. This is a two-minute fix once you know where to look — but if you do not know this screen, people spend hours deleting and re-creating connections instead.

1
Open Data Source Settings Go to Home → Transform Data → Data Source Settings. Make sure you are on the Data sources in current file tab. You will see all sources the current report is connected to.
2
Select the broken source Click on the data source showing the old or broken path. It will highlight in blue. Then click the Change Source button at the bottom of the dialog.
3
Enter or browse to the new path A small dialog appears showing the current file path. Either type the new path directly or click Browse to navigate to the file. Click OK.
4
Close and Apply Click Close to dismiss Data Source Settings. Power BI will show a yellow notification bar saying "There are pending changes." Click Apply changes or go to Home → Close and Apply in Power Query Editor to re-load the data from the new path.
Change Source — SalesData.xlsx
Excel Workbook
File path
C:\Users\jdoe\Downloads\SalesData.xlsx
Browse...
File not found at this location
New path
C:\Reports\2024\SalesData.xlsx
Browse...
File found
OK
Cancel

Editing Credentials

When a database password changes or you need to switch authentication methods, you update credentials through the Edit Permissions button in Data Source Settings — not by deleting and re-creating the connection. Deleting and re-creating loses all your Power Query steps.

1
Select the source and click Edit Permissions In Data Source Settings, click the data source whose credentials you want to change, then click Edit Permissions at the bottom.
2
The Permissions dialog appears This dialog shows the current credential type and privacy level for that source. Click the Edit button next to the Credentials section to open the credential entry screen.
3
Enter new credentials and save Enter the updated username and password (or switch to a different authentication method). Click Save. Power BI stores the new credentials and will use them on the next refresh — no restart required.
Edit Permissions — SQLSRV01\PRODUCTION · SalesDB
SQLSRV01\PRODUCTION · SalesDB
Credentials
🔑
Database authentication
Username: reports_user · Password: ••••••••
Edit
Privacy Level
Organizational▾
Data can be shared with other Organizational sources
OK
Cancel

Privacy Levels — What They Are and Why They Matter

Privacy levels are one of the most misunderstood settings in Power BI. They control whether data from one source is allowed to be combined with data from another source during query folding and cross-source joins. Set them wrong and your queries get blocked. Leave them all on None and Power BI asks you to set them every time you refresh.

Privacy Level What it means When to use it
Public The data is public knowledge and can be combined freely with any other source Public datasets, open government data, Wikipedia tables
Organizational Data can be shared with other Organizational-level sources but not with Public sources Internal company databases, corporate SharePoint, company-wide Excel files
Private Data is sensitive and cannot be combined with any other source without explicit permission — causes the Formula.Firewall error when mixing with other levels Personal salary data, client PII, confidential financial records
None No privacy level assigned — Power BI will prompt you to set one before it can combine this source with others Newly added sources before you have decided their classification

The Formula.Firewall Error

The Formula.Firewall error is one of the most common errors beginners hit in Power BI — and it is caused entirely by privacy level mismatches. Understanding it once means you will never be confused by it again.

Formula.Firewall Error
DataSource.Error: Formula.Firewall: Query references other queries or steps that access different data sources. Please rebuild this data combination.
What is happening: Power BI is trying to combine data from two sources that have different or incompatible privacy levels. It refuses to send data from a Private source to a Public or Organizational source — or vice versa — because it cannot verify whether that cross-source data sharing is safe.

There are two ways to resolve Formula.Firewall errors. The right fix depends on whether you are working with genuinely sensitive data or just learning and building reports with non-sensitive data.

Fix 1 — Set matching privacy levels
Open Data Source Settings → Edit Permissions for each source involved in the error. Set all sources to the same privacy level — typically Organizational for internal company data. When all sources share a level, Power BI allows them to be combined freely.
Fix 2 — Ignore privacy levels globally
Go to File → Options and Settings → Options → Privacy and set it to "Always ignore Privacy Level settings". This disables the firewall entirely. Only appropriate for learning or when all your data sources are already fully internal and safe.

Teacher's Note: In Lesson 4 we turned off privacy levels globally in the Options settings to prevent this error while learning. That was the right call for a learning environment. In a real production report connecting to external APIs alongside internal databases, you should take the time to set proper privacy levels per source rather than ignoring them — it is a genuine data security boundary.

Clearing Permissions

The Clear Permissions button removes the stored credentials for a data source without removing the connection itself. Power BI will prompt you to re-authenticate the next time it tries to access that source. This is useful when you need to switch accounts or when stored credentials have become stale after an IT password reset.

When to use Clear Permissions vs Change Source:

CLEAR PERMISSIONS — use when:
  - Your database password was reset by IT
  - You want to authenticate with a different account
  - Refresh fails with "Access denied" despite correct path
  - You want to be prompted to re-enter credentials fresh

CHANGE SOURCE — use when:
  - The source file has been moved to a new folder
  - The source file has been renamed
  - A database server has been migrated to a new address
  - You are switching from a test database to production

DO NOT delete and re-create the connection — you will lose
all Power Query transformation steps applied to that query.
Quick decision guide
"File not found" error
→ Use Change Source to update the file path
"Access denied" or credential error
→ Use Clear Permissions then re-enter credentials
Formula.Firewall error
→ Use Edit Permissions to match privacy levels across sources
Password changed by IT
→ Use Clear Permissions then enter the new password when prompted

The Pending Changes Banner

Any time you make a change in Data Source Settings — a new path, updated credentials, or a privacy level change — Power BI does not immediately re-load the data. It waits. A yellow banner appears at the top of the Power Query Editor window prompting you to apply the changes. Do not ignore this banner.

Power BI Desktop — SalesReport.pbix
⚠️ There are pending changes in your queries that haven't been applied.
Apply changes
Discard changes
Report canvas — data not yet refreshed with new source settings

Data Source Settings on Power BI Service

Everything covered so far applies to Power BI Desktop. When you publish a report to Power BI Service and set up a scheduled refresh, the Service has its own separate data source settings. Credentials stored in Desktop are never transferred — you must configure them again in the Service.

Setting In Desktop In Service
Where to find it Home → Transform Data → Data Source Settings Workspace → Datasets → Settings → Gateway and Cloud Connections
Credentials Stored locally on your machine only Must be entered separately — not copied from Desktop on publish
File paths Local file paths work fine in Desktop Local file paths do not work in Service — must use SharePoint, OneDrive, or a Gateway
On-premises databases Connect directly — Desktop is on the same network Requires an On-premises Data Gateway to be installed and configured

Teacher's Note: The single most common reason why a report refreshes perfectly in Desktop but fails the moment it is published to Service is that local file paths do not exist on Microsoft's cloud servers. If your source is a file, move it to SharePoint or OneDrive and update the connection before publishing. Power BI Service can access SharePoint and OneDrive natively without any additional gateway setup.

Practice

Practice 1 of 3

After moving a source Excel file to a new folder, you fix the broken connection in Power BI by going to Data Source Settings and clicking ___ Source.

Practice 2 of 3

The Formula.___ error appears in Power BI when you try to combine data from sources with incompatible privacy level settings.

Practice 3 of 3

When you publish a report to Power BI Service, credentials stored in Desktop are ___ transferred automatically — you must enter them again in Service under Dataset Settings.

Lesson Quiz

Quiz 1 of 3

You have a report connected to a company SQL Server database and a public government CSV file. After adding a merge between the two, you receive a Formula.Firewall error. What is the most appropriate fix?

Quiz 2 of 3

Your IT team reset the password for the SQL database account used by your Power BI report. What is the correct action to take in Power BI Desktop?

Quiz 3 of 3

You publish a report to Power BI Service that is connected to a file at C:\Reports\SalesData.xlsx. The scheduled refresh in Service fails immediately. What is the root cause?

Next up — Lesson 9 covers Data Types in depth — why getting data types right before you build anything is critical, how Power BI detects them automatically, when it gets them wrong, and exactly how to fix every common data type problem in Power Query Editor.

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