OData and REST API connections in Power BI - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is OData in the context of Power BI?

OData is a web protocol that allows Power BI to connect and fetch data from online sources using a standard URL format. It makes data access easy and consistent.

beginner

What does REST API stand for and how is it used in Power BI?

REST API stands for Representational State Transfer Application Programming Interface. Power BI uses it to get data from web services by sending requests and receiving data in formats like JSON.

beginner

How do you connect to an OData feed in Power BI?

In Power BI Desktop, go to 'Get Data', choose 'OData Feed', then enter the OData URL. Power BI will connect and show available tables to load.

beginner

What is a common data format returned by REST APIs for Power BI?

JSON (JavaScript Object Notation) is the most common data format returned by REST APIs, which Power BI can parse and convert into tables.

intermediate

Why is authentication important when connecting to REST APIs in Power BI?

Authentication ensures only authorized users can access the data. Power BI supports methods like API keys or OAuth to securely connect to REST APIs.

Which protocol does Power BI use to connect to an OData feed?

A HTTP/HTTPS

B FTP

C SMTP

D SSH

OData feeds use HTTP or HTTPS protocols to transfer data over the web.

What data format does a REST API commonly return for Power BI to consume?

A XML

B CSV

C JSON

D TXT

REST APIs commonly return data in JSON format, which Power BI can easily parse.

Which Power BI feature allows you to connect directly to a REST API?

A Get Data > Excel

B Get Data > Web

C Get Data > Folder

D Get Data > SQL Server

The 'Web' connector in Power BI lets you connect to REST APIs by entering the API URL.

What is the main purpose of authentication when connecting to REST APIs?

A To secure data access

B To speed up data transfer

C To format data

D To compress data

Authentication ensures that only authorized users can access the API data.

Which of these is NOT a typical step when connecting to an OData feed in Power BI?

A Entering the OData URL

B Authenticating if required

C Selecting tables to load

D Writing SQL queries

You do not write SQL queries when connecting to OData feeds; you select tables from the feed.

Explain how Power BI connects to data using OData feeds and what makes OData useful.

Think about how you open a website and see data organized in tables.

Describe the process and key considerations when connecting Power BI to a REST API.

Imagine ordering data from a web service and needing permission to get it.

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