Why OData and REST API connections in Power BI? - Purpose & Use Cases

The Big Idea

What if your reports could update themselves while you focus on decisions?

The Scenario

Imagine you need to gather sales data from multiple online services every day. You open each website, copy the numbers, paste them into a spreadsheet, and try to keep track of updates manually.

The Problem

This manual method is slow and tiring. You risk making mistakes copying data, miss updates, and waste hours repeating the same boring tasks. It's hard to keep data fresh and reliable.

The Solution

Using OData and REST API connections lets Power BI automatically fetch data from online services. It updates your reports with fresh data instantly, without any manual copying or pasting.

Before vs After

✗ Before

Open website > Copy data > Paste in Excel > Repeat daily

✓ After

Connect to OData URL in Power BI > Refresh data with one click

What It Enables

You can build live dashboards that update automatically, giving you real-time insights without extra work.

Real Life Example

A marketing team connects Power BI to their social media platform's REST API to track campaign performance daily, saving hours and spotting trends faster.

Key Takeaways

Manual data collection is slow and error-prone.

OData and REST APIs automate data fetching into Power BI.

This saves time and keeps reports always up to date.

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