OData and REST API connections in Power BI - Dashboard Guide

Dashboard Mode - OData and REST API connections

Business Question

How can we connect Power BI to online data sources using OData and REST API to create a live sales dashboard?

Sample Data

Data is fetched live from an OData feed and a REST API providing sales orders and customer info.

OrderID	Customer	OrderDate	SalesAmount	Region
1001	Alpha Co	2024-01-15	250	North
1002	Beta LLC	2024-01-20	400	East
1003	Gamma Inc	2024-02-05	150	South
1004	Alpha Co	2024-02-10	300	North
1005	Delta Ltd	2024-02-15	500	West

Dashboard Components

• KPI Card: Total Sales - Shows total sales amount from all orders.
  Formula: Total Sales = SUM(Sales[SalesAmount])
  Result: 1600
• Bar Chart: Sales by Region - Displays sales totals grouped by region.
  Data: Sum of SalesAmount by Region
• Table: Recent Orders - Lists OrderID, Customer, OrderDate, and SalesAmount.
  Shows latest 5 orders from the connected data.

Dashboard Layout

+----------------------+----------------------+
|      Total Sales      |    Sales by Region   |
|       (KPI Card)      |      (Bar Chart)     |
+----------------------+----------------------+
|                  Recent Orders                |
|                    (Table)                   |
+----------------------------------------------+
  

Interactivity

A slicer filters data by Region. Selecting a region updates the Total Sales KPI, the Sales by Region bar chart (highlighting the selected region), and the Recent Orders table to show only orders from that region.

Data refreshes automatically from the OData and REST API sources when the dashboard is opened or refreshed, ensuring live data.

Self Check

Add a filter for Region = North. Which components update and what changes occur?

• Total Sales: Updates to sum sales only for North region orders (250 + 300 = 550).
• Sales by Region: Highlights North region bar; other regions dim.
• Recent Orders: Shows only orders with Region = North (OrderID 1001 and 1004).

Key Result

A Power BI dashboard connecting live sales data via OData and REST API showing total sales, sales by region, and recent orders with region filtering.

Practice

1. What is the main advantage of using an OData connection in Power BI compared to a generic REST API?

easy

A. It cannot refresh data automatically.

B. It requires manual coding for every data request.

C. It only works with Excel files.

D. It provides a standardized query language and easier data filtering.

Solution

1. Step 1: Understand OData protocol features

   OData supports standardized query options like filtering, sorting, and paging directly in the URL.

2. Step 2: Compare with REST API flexibility

   REST APIs are flexible but often require custom query parameters and manual handling of data requests.

3. Final Answer:

   It provides a standardized query language and easier data filtering. -> Option D

4. Quick Check:

   OData = Standardized queries [OK]

Hint: OData uses standard queries; REST APIs need custom calls [OK]

Common Mistakes:

• Thinking OData only works with Excel
• Assuming REST APIs auto-refresh data
• Believing OData requires manual coding

2. Which Power Query M function is used to connect to a REST API endpoint in Power BI?

easy

A. OData.Feed()

B. Web.Contents()

C. Csv.Document()

D. Excel.Workbook()

Solution

1. Step 1: Identify function for REST API calls

   The Web.Contents() function fetches data from any web URL, including REST APIs.

2. Step 2: Differentiate from OData function

   OData.Feed() is specific for OData sources, not generic REST APIs.

3. Final Answer:

   Web.Contents() -> Option B

4. Quick Check:

   REST API = Web.Contents() [OK]

Hint: Use Web.Contents() for REST API URLs [OK]

Common Mistakes:

• Using OData.Feed() for REST APIs
• Confusing CSV import with API calls
• Trying Excel.Workbook() for web data

3. Given this Power Query M code snippet connecting to an OData feed:

let
  Source = OData.Feed("https://services.odata.org/V4/Northwind/Northwind.svc/Products"),
  Filtered = Table.SelectRows(Source, each [CategoryID] = 1)
in
  Filtered

What will be the result?

medium

A. An empty table because CategoryID is not a valid column.

B. An error because OData.Feed cannot filter data.

C. A table of products where CategoryID equals 1.

D. A list of all categories instead of products.

Solution

1. Step 1: Understand OData.Feed output

   The OData.Feed() function returns a table of products from the OData service.

2. Step 2: Analyze filtering step

   Table.SelectRows() filters rows where CategoryID equals 1, which is valid for this dataset.

3. Final Answer:

   A table of products where CategoryID equals 1. -> Option C

4. Quick Check:

   Filter by CategoryID=1 = filtered product table [OK]

Hint: OData.Feed returns tables; filter with Table.SelectRows() [OK]

Common Mistakes:

• Assuming OData.Feed cannot filter
• Confusing products with categories
• Thinking CategoryID column is missing

4. You wrote this Power Query M code to get data from a REST API:

let
  Source = Web.Contents("https://api.example.com/data"),
  Json = Json.Document(Source),
  Table = Table.FromList(Json, Splitter.SplitByNothing())
in
  Table

But you get an error saying "Expression.Error: We cannot convert the value to a table." What is the likely cause?

medium

A. The JSON returned is an object, not a list, so Table.FromList fails.

B. Web.Contents() cannot fetch JSON data.

C. Json.Document() only works with XML data.

D. Splitter.SplitByNothing() is not a valid function.

Solution

1. Step 1: Check JSON structure expected

   Table.FromList() expects a list, but if JSON is an object (record), it cannot convert directly.

2. Step 2: Understand error cause

   The error means the JSON is not a list but an object, so conversion fails.

3. Final Answer:

   The JSON returned is an object, not a list, so Table.FromList fails. -> Option A

4. Quick Check:

   JSON object ≠ list causes conversion error [OK]

Hint: Check if JSON is list or object before Table.FromList() [OK]

Common Mistakes:

• Thinking Web.Contents() can't get JSON
• Assuming Json.Document() only parses XML
• Believing Splitter.SplitByNothing() is invalid

5. You want to combine data from an OData feed and a REST API in Power BI. The OData feed provides product details, and the REST API returns live stock levels as JSON. Which approach is best to create a unified table for reporting?

hard

A. Use OData.Feed() to get products, Web.Contents() + Json.Document() for stock, then merge tables in Power Query.

B. Use only OData.Feed() for both sources since it supports all APIs.

C. Import REST API JSON as CSV and append to OData feed table directly.

D. Load both sources separately and create relationships in the data model without merging.

Solution

1. Step 1: Connect to each data source appropriately

   Use OData.Feed() for the OData product details and Web.Contents() with Json.Document() to parse REST API stock JSON.

2. Step 2: Combine data in Power Query

   Merge the two tables on product ID to create a unified table before loading into the report.

3. Final Answer:

   Use OData.Feed() to get products, Web.Contents() + Json.Document() for stock, then merge tables in Power Query. -> Option A

4. Quick Check:

   Combine sources with correct connectors and merge [OK]

Hint: Use correct connectors per source, then merge in Power Query [OK]

Common Mistakes:

• Trying to use OData.Feed() for REST API JSON
• Appending JSON as CSV without parsing
• Not merging data, just relating tables