Author: Dominick Raimato Page 4 of 5

Earlier this week I spoke about the Basics of Connecting to REST APIs at the Global Power BI Summit. A lot of people found it valuable, but wanted to know more about how to use the POST method to get data. Specifically, they wanted to know how to add a payload with the request to make it work. Since there was a lot of interest, I decided to write an article on this topic and share it with everyone.

For this article, I will be using the Microsoft OAuth2 endpoint to get an authorization token. You can find detailed documentation on the endpoint here. I will not be going into the details of the process to create an app registration or apply it in the Microsoft environment as that will take some time to cover. Instead, I decided to focus on the most important part of the request – the POST Method!

No/Low Code No More!

For many, this will be the scariest part of the entire process. This might be your first time ever writing code for a query from scratch. We do not have a connector to help us with this process. Fear not as we will walk through this entire process together and break it down. So to get everything started, go to Get Data and select Blank Query.

Once you select Blank Query, you will be redirected into Power Query with a blank canvas. I like to quickly update the query name on the right hand side before I forget. I am calling mine “Get-AuthToken”. Once that is in place, we will open up the Advanced Editor in the home ribbon. That is where the real fun will begin…

POST Method Query

Now that the Advanced Editor open, we are going to start writing out the query. We will need to write out a web connector query and a message body to make this work. I like to start with the web connector and build out from there.

Building the Initial Connection Query

Currently, we have Source = “” in our editor window. Those quotes are going to be the base of our query. We are going to start by adding the endpoint url in between the quotes. We should see something that looks like this:

let
    Source = "https://login.microsoftonline.com/<TENANTID>/oauth2/v2.0/token"
in
    Source

In order to specify how we are connecting to the endpoint, we will wrap it with Web.Contents:

let
    Source = Web.Contents("https://login.microsoftonline.com/<TENANTID>/oauth2/v2.0/token")
in
    Source

After that is in place, we need to add our headers. These are specified in the documentation and will be unique to your API. This example uses two headers and they are required to achieve the desired result. Note the comma between the url and the headers.

let
    Source = Web.Contents("https://login.microsoftonline.com/<TENANTID>/oauth2/v2.0/token", [Headers=[Accept="application/json", ContentType="application/x-www-form-urlencoded"]])
in
    Source

Lastly, because the header is specifying the response in JSON, we will wrap the entire string with Json.Document to translate the response.

let
    Source = Json.Document(Web.Contents("https://login.microsoftonline.com/<TENANTID>/oauth2/v2.0/token", [Headers=[Accept="application/json", ContentType="application/x-www-form-urlencoded"]]))
in
    Source

With that code in place we have our base query built. If you want to save some typing, you could always use an existing query as a template. Just copy and paste it into the blank query and make your changes.

Now that we have the base query written out it is time to focus on the message body.

Body Building without Protein

The body comes by a few different names. You might see it as message body, query, payload, or simply “The Data”. Essentially, it is additional information that is passed so the endpoint works as expected. While you don’t have to lift weights for this step, you might find it just as frustrating. I have tried this a few different ways, but found this to be the easiest method.

The first thing we will do is create a line right above our Source line and below the let line. From here, we will enter ContentBody = “”, as a place holder. Make sure you add the comma at the end of the line!

let
    ContentBody = "",
    Source = Json.Document(Web.Contents("https://login.microsoftonline.com/<TENANTID>/oauth2/v2.0/token", [Headers=[Accept="application/json", ContentType="application/x-www-form-urlencoded"]]))
in
    Source

My example requires five different fields be specified in the body. The formula is simple: field name = field data. We will add an ampersand at the end of the line and return to the next line to make it easier to read.

let
    ContentBody = 
        "Content-Type=application/x-www-form-urlencoded&
        scope=https://graph.microsoft.com/.default&
        grant_type=client_credentials&
        client_id=<CLIENTID>&
        client_secret=<CLIENTSECRET>",
    Source = Json.Document(Web.Contents("https://login.microsoftonline.com/<TENANTID>/oauth2/v2.0/token", [Headers=[Accept="application/json", ContentType="application/x-www-form-urlencoded"]]))
in
    Source

As a best practice, I keep elements that might need to be changed at the bottom for easier access. This example leverages a client secret that will need to be updated over time. To make it easier to access, I leave it at the bottom.

Add the Body to the Web Connector

To finalize your query using the POST Method, you have to add the message body to the source line. We need to pass the body as content. However, I need to convert it into binary. We are just going to add Content=Text.ToBinary(ContentBody) inside of the first set of brackets so it passes the body in the web connector.

let
    ContentBody = 
        "Content-Type=application/x-www-form-urlencoded&
        scope=https://graph.microsoft.com/.default&
        grant_type=client_credentials&
        client_id=<CLIENTID>&
        client_secret=<CLIENTSECRET>",
    Source = Json.Document(Web.Contents("https://login.microsoftonline.com/<TENANTID>/oauth2/v2.0/token", [Content=Text.ToBinary(ContentBody), Headers=[Accept="application/json", ContentType="application/x-www-form-urlencoded"]]))
in
    Source

Now that everything is in place, we can click Done and let the query do its magic!

To take things to the next level, I can drill down on the actual token by right clicking and selecting drill down. Next I will convert the query to a function by adding ()=> above the let line. In doing so, I will be able to leverage it for multiple endpoints that require token based authentication with a simple call.

()=>
let
    ContentBody = 
        "Content-Type=application/x-www-form-urlencoded&
        scope=https://graph.microsoft.com/.default&
        grant_type=client_credentials&
        client_id=<CLIENTID>&
        client_secret=<CLIENTSECRET>",
    Source = Json.Document(Web.Contents("https://login.microsoftonline.com/<TENANTID>/oauth2/v2.0/token", [Content=Text.ToBinary(ContentBody), Headers=[Accept="application/json", ContentType="application/x-www-form-urlencoded"]])),
    access_token = Source[access_token]
in
    Source

Make Life Easier with Parameters

I plan to write a more detailed article on Parameters inside Power Query but I want to share a little tip that will make your life much easier. With this example, we are connecting to an app registration inside Azure Active Directory through a Client ID and Client Secret. The Client Secret will expire at some point and needs to be refreshed. To make your life easier, you can add your dynamic values as Parameters so you can update the query quickly.

Go to your home ribbon and click Manage Parameters. Click new and add your parameter name. Lastly, add your parameter value and click OK when finished.

Now we just need to replace the values in our query. We will have to use the ampersands to concatenate our values together so they come together in a single string.

()=>
let
    ContentBody = 
        "Content-Type=application/x-www-form-urlencoded&
        scope=https://graph.microsoft.com/.default&
        grant_type=client_credentials&
    	client_id=" & ClientId & "&
        client_secret=" & ClientSecret ,
    Source = Json.Document(Web.Contents("https://login.microsoftonline.com/" & TenantId & "/oauth2/v2.0/token", [Content=Text.ToBinary(ContentBody), Headers=[Accept="application/json", ContentType="application/x-www-form-urlencoded"]])),
    access_token = Source[access_token]
in
    access_token

Now if I need to update my client secret, I can just update the parameter instead of breaking open the Advanced Editor. I can even do it from the settings view in the Power BI Service. But that will have to wait for another article.

Final Thoughts on the POST Method

It is important to note that not all POST Method endpoints are meant for querying in Power BI. The primary purpose of the method is to create items. However, it is not unheard of for querying rows of data. Before you do anything with an endpoint that uses the POST Method make sure you review the documentation. You might accidentally write data to your endpoint if you are not careful!

Do you have a use case for querying using the POST Method? Any favorite endpoints? If so, leave a comment below!

In my last article, I shared how to scale a query by using a function in Power Query. However, I noted there might be some challenges with this approach and considerations you should keep in mind when connecting to REST APIs. Some of these considerations are simple and are similar to normal query optimization activities. While not as technical as other articles, I feel it is important to take some time to focus on potential challenges you might encounter when leveraging REST APIs.

Limits, Throttling, and Speed

When reading your documentation, you might see words such as “limits” and “throttling” and wonder what they are. You will build your report and everything will be fine until one day your refresh fails. In reviewing the refresh errors it will suddenly make sense what “limits” and “throttling” mean.

To ensure APIs are not overburdened, limits and throttling are employed to prevent abuse. This protects the endpoints and provides a reliable service. Understanding how to navigate them are essential to prevent your refreshes from failing as your solution scales.

What are API Request Limits?

API limits restrict the number of calls made in a day, week, or month. If you signed up for the Yahoo Finance API, you notice they have three tiers of membership. The free tier limits your calls to 100 per day. Because of how we built our function, you would have to limit your report to 100 stocks and only refresh it once a day.

Now there are additional tiers that you can purchase which increase your limits. The Yahoo Finance API offers tiers that give you 20,000 or 75,000 calls per month which might help accommodate your use case but requires an additional financial investment. But even if you increase your subscription, note that these tiers still have a hard limit. Meaning that you might need to keep purchasing a higher tier if you blow through your request limit.

To be a good steward of your subscription, you will want to regularly monitor your API usage and verify that you are not burning through your quotas too quickly. It never fails – you run out of requests just when you need the data the most.

What is Throttling?

APIs use throttling to protect endpoints from being heavily queried over a short period of time. Queries are limited to the number of calls made per minute, per 15 minute window, or per hour. This protects endpoints from rogue code that could degrade the service because of abuse.

With the Yahoo Finance API, our documentation states that there is a rate limit of 300 calls per minute. If you had a list of 1,200 stocks it would take at least four minutes for the refresh to complete. (1,200 stocks divided by 300 = 4 minutes) Just like how every API is unique, they manage throttling differently.

Last year I built a Power BI report that leveraged Google’s mapping APIs to get coordinates and street views of addresses in my town. Google enacted throttling to limit requests to 100 per minute. When refreshing my data, I hit my 100 request limit and the API paused until the full minute had passed. In doing so, I was able to proceed with the refresh. With 3,500 houses in town, it took 35 minutes for the refresh to complete. It was slow, but it worked great.

On the other side of the spectrum, the Microsoft Graph APIs have a limit of 10,000 calls per 10 minute period. When I ran over this limit, instead of the API pausing, I ended up receiving responses with a 429 error stating I reached the throttling limits. In order to manage this, I had to get a little more creative with my query to make sure I did not receive that error.

Impact on Refresh Time

Regardless of limits, you will need to consider refresh time when using REST APIs. If your primary data sources reside in SQL servers, this will be an adjustment for you. Normally you just cast a wide net with your query and bring in everything you can and work from there. With APIs, you want to narrow that scope to only what you really need. But with REST APIs, the refreshes tend to be slower. Adding some filtering will speed up your queries and make them more efficient.

If you are in a situation where you need a large amount of data from an API, you might want to consider leveraging Azure Data Factory or Databricks to incrementally replicate that data into a data warehouse instead.

Paging Queries

For this series of articles, our endpoint was fairly basic. It only brought back one row of data for each stock symbol. This was by design because our overall goal was to cover the basics. As you explore other APIs, you might find endpoints that bring back several rows at a time.

If you expand your horizon with REST APIs, eventually you are going to run into something called paging. Simply put, paging is the splitting of responses over multiple queries. Similar to limits, this is to prevent overburdening the endpoint with your query.

As an example, let’s say you are querying an endpoint that has 50,000 records. Paging has been enabled on this query and is limiting the responses to 1,000 records at a time. In order to receive all 50,000 records, you will need to build logic into your query to pull each page individually.

So how do you know your endpoint is using paging? It is all about the documentation. If an endpoint has pagination, there are usually a few parameters that will tip you off. If you see a parameter called “PageNo”, “PageSize”, or “Top”, you could run into paging.

It is also important to consider that you could avoid pagination with quality filtering. If your request is targeted and removes the noise of other records, it could avoid this problem all together.

In the coming weeks I will be doing an article specifically on paging, so keep an eye out for it!

Token Authentication

Another challenge you might encounter is token based authentication. Instead of passing an API key for authentication, you would need to call another endpoint to receive a token. Once you have the token, you would pass it through a header.

If you encounter this situation, you would need to create a function in Power Query that would solely return a token. While it takes a few extra steps, it is likely reusable with other endpoints in your report. In addition to that, it will simplify your query code and keep it tight and compact.

Conclusion

Congratulations for making it to the end of this series. There are a lot of challenges when implementing REST APIs as a data source but the juice is worth the squeeze. Taking yourself out of the mix and automating my refreshes is the end goal. And while the experience may not be as efficient as a SQL data source, it still gets the job done.

Have you been following along? Were you able to successfully connect and extract data from Yahoo Finance? How about other REST APIs? Let me know in the comments below!

In my last article, I showed you how to connect the quote endpoint from the Yahoo Finance API to Power BI. By leveraging the documentation and using copy/paste, we successfully connected to the API without a single line of code. In our review of the outcome we noted that our response only brought back data for a single stock.

While helpful, we know you probably want to refresh data for more than one stock. In fact, I happen to have a list of stocks that I am currently watching:

My next challenge is to take my original query and make it sustainable for however many stocks I have on my watch list.

Options are Plentiful

As with every Microsoft product, I have several different ways that I could manage this challenge. All have their benefits and drawbacks. Let’s look at them each and see which one would work best for my scenario.

Option 1 – Append Individual Queries

The first solution you might have considered is building a separate connection for each of the individual stocks we have in our list. Each query would be individually created and then appended into a master list so that way it stays organized. This solution would work and be effective, but there are drawbacks.

First of all, the biggest draw back is that I have to manually create this query each and every time I want to add a new stock. This does not take a ton of time, but it would require a few minutes of effort each and every time. Not a big deal if you only need to add one or two stocks to the model but it would add up with 20-30 stocks.

The other drawback is that you will have to continue managing the data model. If the list of stocks is dynamic, that means you either need to create a single model with every single stock in it or continue to manage it over time. This is not really sustainable as new stocks enter the market on a regular basis and requires manual maintenance.

Option 2 – Go Back to the Documentation

Sometimes you have some options when it comes to your endpoints for expanding your query. If we go back to look at our documentation for the quote endpoint, you will see that we can specify up to 10 stock symbols in our query.

Perfect! So instead of having to write out 25 separate queries, I can condense it all into three. That is much more manageable and efficient! Well – almost more efficient…

Remember what I stated above – because we are still specifying the stock symbols for each query we still have to manually intervene every time we make a change to our stock list. This could get difficult especially as we go to maintain our list over time as we might need to remove stocks later. As a result, we will spend time searching for which query to resolve.

Option 3 – Scale Out our Original Query as a Function

The last option we have is to make our current query scalable. How do we make a query scalable? By converting it into a function.

Functions allow us to reuse that query over and over again to simplify our refresh. Acting similar to our first option, we can apply a function to a list of stock symbols and quickly bring back the quote information. Now instead of managing the queries, we are just managing a list of stock symbols. As symbols are added and removed, our data model adjusts accordingly. The result allows us to automate refreshes without having to adjust the data model in the future.

Converting a Query to a Function

Remember how I said you might need some minimal coding? That time has come. We will need to do something you may have never done before – open the advanced editor window in Power Query.

Before we do that, I do want to rename the current query to “Get-StockInfo” so it is a little easier to read. Just update the name on the query settings bar on the right. I like using the word get in front to help quickly identify it as a function versus a query.

Once you have done that, click on Advanced Editor in the home ribbon and strap in for the ride!

Step 1 – Convert the Query to a Function

Our goal is to make this function flexible for any stock symbol. That means we need to require a stock symbol to be called every time the function is leveraged.

When you open the code editor, the first line has the single word “let”. We are going to insert a row above that and put a pair of parentheses followed by an equals sign and greater than sign. This effectively makes the conversion from a query to a function.

()=>
let
    Source = Json.Document(Web.Contents("https://yfapi.net/v6/finance/quote?region=US&lang=en&symbols=MSFT", [Headers=[Accept="application/json", #"X-API-KEY"="bHjSKbiRtr4cOzmOopdrI5TUKX5kMKXU6weUteeL"]])),
    #"Converted to Table" = Table.FromRecords({Source}),
    #"Expanded quoteResponse" = Table.ExpandRecordColumn(#"Converted to Table", "quoteResponse", {"result", "error"}, {"quoteResponse.result", "quoteResponse.error"}),
    #"Expanded quoteResponse.result" = Table.ExpandListColumn(#"Expanded quoteResponse", "quoteResponse.result"),
    #"Expanded quoteResponse.result1" = Table.ExpandRecordColumn(#"Expanded quoteResponse.result", "quoteResponse.result", {"language", "region", "quoteType", "quoteSourceName", "triggerable", "currency", "firstTradeDateMilliseconds", "postMarketChangePercent", "postMarketTime", "postMarketPrice", "postMarketChange", "regularMarketChange", "regularMarketChangePercent", "regularMarketTime", "regularMarketPrice", "regularMarketDayHigh", "regularMarketDayRange", "regularMarketDayLow", "regularMarketVolume", "regularMarketPreviousClose", "bid", "ask", "bidSize", "askSize", "fullExchangeName", "financialCurrency", "regularMarketOpen", "averageDailyVolume3Month", "averageDailyVolume10Day", "fiftyTwoWeekLowChange", "fiftyTwoWeekLowChangePercent", "fiftyTwoWeekRange", "fiftyTwoWeekHighChange", "fiftyTwoWeekHighChangePercent", "fiftyTwoWeekLow", "fiftyTwoWeekHigh", "dividendDate", "marketState", "earningsTimestamp", "earningsTimestampStart", "earningsTimestampEnd", "trailingAnnualDividendRate", "trailingPE", "trailingAnnualDividendYield", "epsTrailingTwelveMonths", "epsForward", "epsCurrentYear", "priceEpsCurrentYear", "sharesOutstanding", "bookValue", "fiftyDayAverage", "fiftyDayAverageChange", "fiftyDayAverageChangePercent", "twoHundredDayAverage", "twoHundredDayAverageChange", "twoHundredDayAverageChangePercent", "marketCap", "forwardPE", "priceToBook", "sourceInterval", "exchangeDataDelayedBy", "pageViewGrowthWeekly", "averageAnalystRating", "tradeable", "priceHint", "exchange", "shortName", "longName", "messageBoardId", "exchangeTimezoneName", "exchangeTimezoneShortName", "gmtOffSetMilliseconds", "market", "esgPopulated", "displayName", "symbol"}, {"language", "region", "quoteType", "quoteSourceName", "triggerable", "currency", "firstTradeDateMilliseconds", "postMarketChangePercent", "postMarketTime", "postMarketPrice", "postMarketChange", "regularMarketChange", "regularMarketChangePercent", "regularMarketTime", "regularMarketPrice", "regularMarketDayHigh", "regularMarketDayRange", "regularMarketDayLow", "regularMarketVolume", "regularMarketPreviousClose", "bid", "ask", "bidSize", "askSize", "fullExchangeName", "financialCurrency", "regularMarketOpen", "averageDailyVolume3Month", "averageDailyVolume10Day", "fiftyTwoWeekLowChange", "fiftyTwoWeekLowChangePercent", "fiftyTwoWeekRange", "fiftyTwoWeekHighChange", "fiftyTwoWeekHighChangePercent", "fiftyTwoWeekLow", "fiftyTwoWeekHigh", "dividendDate", "marketState", "earningsTimestamp", "earningsTimestampStart", "earningsTimestampEnd", "trailingAnnualDividendRate", "trailingPE", "trailingAnnualDividendYield", "epsTrailingTwelveMonths", "epsForward", "epsCurrentYear", "priceEpsCurrentYear", "sharesOutstanding", "bookValue", "fiftyDayAverage", "fiftyDayAverageChange", "fiftyDayAverageChangePercent", "twoHundredDayAverage", "twoHundredDayAverageChange", "twoHundredDayAverageChangePercent", "marketCap", "forwardPE", "priceToBook", "sourceInterval", "exchangeDataDelayedBy", "pageViewGrowthWeekly", "averageAnalystRating", "tradeable", "priceHint", "exchange", "shortName", "longName", "messageBoardId", "exchangeTimezoneName", "exchangeTimezoneShortName", "gmtOffSetMilliseconds", "market", "esgPopulated", "displayName", "symbol"})
in
    #"Expanded quoteResponse.result1"

However, we have not done anything to handle the requirement to pass a stock symbol when the function is called. To require a stock symbol be called, we will simply add a variable called StockSymbol and specify that it be passed in a text format. This will require a stock symbol be passed any time you leverage this function.

(StockSymbol as text)=>
let
    Source = Json.Document(Web.Contents("https://yfapi.net/v6/finance/quote?region=US&lang=en&symbols=MSFT", [Headers=[Accept="application/json", #"X-API-KEY"="bHjSKbiRtr4cOzmOopdrI5TUKX5kMKXU6weUteeL"]])),
    #"Converted to Table" = Table.FromRecords({Source}),
    #"Expanded quoteResponse" = Table.ExpandRecordColumn(#"Converted to Table", "quoteResponse", {"result", "error"}, {"quoteResponse.result", "quoteResponse.error"}),
    #"Expanded quoteResponse.result" = Table.ExpandListColumn(#"Expanded quoteResponse", "quoteResponse.result"),
    #"Expanded quoteResponse.result1" = Table.ExpandRecordColumn(#"Expanded quoteResponse.result", "quoteResponse.result", {"language", "region", "quoteType", "quoteSourceName", "triggerable", "currency", "firstTradeDateMilliseconds", "postMarketChangePercent", "postMarketTime", "postMarketPrice", "postMarketChange", "regularMarketChange", "regularMarketChangePercent", "regularMarketTime", "regularMarketPrice", "regularMarketDayHigh", "regularMarketDayRange", "regularMarketDayLow", "regularMarketVolume", "regularMarketPreviousClose", "bid", "ask", "bidSize", "askSize", "fullExchangeName", "financialCurrency", "regularMarketOpen", "averageDailyVolume3Month", "averageDailyVolume10Day", "fiftyTwoWeekLowChange", "fiftyTwoWeekLowChangePercent", "fiftyTwoWeekRange", "fiftyTwoWeekHighChange", "fiftyTwoWeekHighChangePercent", "fiftyTwoWeekLow", "fiftyTwoWeekHigh", "dividendDate", "marketState", "earningsTimestamp", "earningsTimestampStart", "earningsTimestampEnd", "trailingAnnualDividendRate", "trailingPE", "trailingAnnualDividendYield", "epsTrailingTwelveMonths", "epsForward", "epsCurrentYear", "priceEpsCurrentYear", "sharesOutstanding", "bookValue", "fiftyDayAverage", "fiftyDayAverageChange", "fiftyDayAverageChangePercent", "twoHundredDayAverage", "twoHundredDayAverageChange", "twoHundredDayAverageChangePercent", "marketCap", "forwardPE", "priceToBook", "sourceInterval", "exchangeDataDelayedBy", "pageViewGrowthWeekly", "averageAnalystRating", "tradeable", "priceHint", "exchange", "shortName", "longName", "messageBoardId", "exchangeTimezoneName", "exchangeTimezoneShortName", "gmtOffSetMilliseconds", "market", "esgPopulated", "displayName", "symbol"}, {"language", "region", "quoteType", "quoteSourceName", "triggerable", "currency", "firstTradeDateMilliseconds", "postMarketChangePercent", "postMarketTime", "postMarketPrice", "postMarketChange", "regularMarketChange", "regularMarketChangePercent", "regularMarketTime", "regularMarketPrice", "regularMarketDayHigh", "regularMarketDayRange", "regularMarketDayLow", "regularMarketVolume", "regularMarketPreviousClose", "bid", "ask", "bidSize", "askSize", "fullExchangeName", "financialCurrency", "regularMarketOpen", "averageDailyVolume3Month", "averageDailyVolume10Day", "fiftyTwoWeekLowChange", "fiftyTwoWeekLowChangePercent", "fiftyTwoWeekRange", "fiftyTwoWeekHighChange", "fiftyTwoWeekHighChangePercent", "fiftyTwoWeekLow", "fiftyTwoWeekHigh", "dividendDate", "marketState", "earningsTimestamp", "earningsTimestampStart", "earningsTimestampEnd", "trailingAnnualDividendRate", "trailingPE", "trailingAnnualDividendYield", "epsTrailingTwelveMonths", "epsForward", "epsCurrentYear", "priceEpsCurrentYear", "sharesOutstanding", "bookValue", "fiftyDayAverage", "fiftyDayAverageChange", "fiftyDayAverageChangePercent", "twoHundredDayAverage", "twoHundredDayAverageChange", "twoHundredDayAverageChangePercent", "marketCap", "forwardPE", "priceToBook", "sourceInterval", "exchangeDataDelayedBy", "pageViewGrowthWeekly", "averageAnalystRating", "tradeable", "priceHint", "exchange", "shortName", "longName", "messageBoardId", "exchangeTimezoneName", "exchangeTimezoneShortName", "gmtOffSetMilliseconds", "market", "esgPopulated", "displayName", "symbol"})
in
    #"Expanded quoteResponse.result1"

Step 2 – Make the Connection String Dynamic

Now that we converted the query to a function and required a stock symbol be passed, it is time for us to use it dynamically with the connection string.

On line 3, you see our endpoint url and parameters that specify MSFT as our designated stock. We need to replace MSFT with our new variable. We will simply delete the current symbol, add an ampersand (&) outside of the quotes, and specify StockSymbol to concatenate the values together.

(StockSymbol as text)=>
let
    Source = Json.Document(Web.Contents("https://yfapi.net/v6/finance/quote?region=US&lang=en&symbols=" & StockSymbol, [Headers=[Accept="application/json", #"X-API-KEY"="bHjSKbiRtr4cOzmOopdrI5TUKX5kMKXU6weUteeL"]])),
    #"Converted to Table" = Table.FromRecords({Source}),
    #"Expanded quoteResponse" = Table.ExpandRecordColumn(#"Converted to Table", "quoteResponse", {"result", "error"}, {"quoteResponse.result", "quoteResponse.error"}),
    #"Expanded quoteResponse.result" = Table.ExpandListColumn(#"Expanded quoteResponse", "quoteResponse.result"),
    #"Expanded quoteResponse.result1" = Table.ExpandRecordColumn(#"Expanded quoteResponse.result", "quoteResponse.result", {"language", "region", "quoteType", "quoteSourceName", "triggerable", "currency", "firstTradeDateMilliseconds", "postMarketChangePercent", "postMarketTime", "postMarketPrice", "postMarketChange", "regularMarketChange", "regularMarketChangePercent", "regularMarketTime", "regularMarketPrice", "regularMarketDayHigh", "regularMarketDayRange", "regularMarketDayLow", "regularMarketVolume", "regularMarketPreviousClose", "bid", "ask", "bidSize", "askSize", "fullExchangeName", "financialCurrency", "regularMarketOpen", "averageDailyVolume3Month", "averageDailyVolume10Day", "fiftyTwoWeekLowChange", "fiftyTwoWeekLowChangePercent", "fiftyTwoWeekRange", "fiftyTwoWeekHighChange", "fiftyTwoWeekHighChangePercent", "fiftyTwoWeekLow", "fiftyTwoWeekHigh", "dividendDate", "marketState", "earningsTimestamp", "earningsTimestampStart", "earningsTimestampEnd", "trailingAnnualDividendRate", "trailingPE", "trailingAnnualDividendYield", "epsTrailingTwelveMonths", "epsForward", "epsCurrentYear", "priceEpsCurrentYear", "sharesOutstanding", "bookValue", "fiftyDayAverage", "fiftyDayAverageChange", "fiftyDayAverageChangePercent", "twoHundredDayAverage", "twoHundredDayAverageChange", "twoHundredDayAverageChangePercent", "marketCap", "forwardPE", "priceToBook", "sourceInterval", "exchangeDataDelayedBy", "pageViewGrowthWeekly", "averageAnalystRating", "tradeable", "priceHint", "exchange", "shortName", "longName", "messageBoardId", "exchangeTimezoneName", "exchangeTimezoneShortName", "gmtOffSetMilliseconds", "market", "esgPopulated", "displayName", "symbol"}, {"language", "region", "quoteType", "quoteSourceName", "triggerable", "currency", "firstTradeDateMilliseconds", "postMarketChangePercent", "postMarketTime", "postMarketPrice", "postMarketChange", "regularMarketChange", "regularMarketChangePercent", "regularMarketTime", "regularMarketPrice", "regularMarketDayHigh", "regularMarketDayRange", "regularMarketDayLow", "regularMarketVolume", "regularMarketPreviousClose", "bid", "ask", "bidSize", "askSize", "fullExchangeName", "financialCurrency", "regularMarketOpen", "averageDailyVolume3Month", "averageDailyVolume10Day", "fiftyTwoWeekLowChange", "fiftyTwoWeekLowChangePercent", "fiftyTwoWeekRange", "fiftyTwoWeekHighChange", "fiftyTwoWeekHighChangePercent", "fiftyTwoWeekLow", "fiftyTwoWeekHigh", "dividendDate", "marketState", "earningsTimestamp", "earningsTimestampStart", "earningsTimestampEnd", "trailingAnnualDividendRate", "trailingPE", "trailingAnnualDividendYield", "epsTrailingTwelveMonths", "epsForward", "epsCurrentYear", "priceEpsCurrentYear", "sharesOutstanding", "bookValue", "fiftyDayAverage", "fiftyDayAverageChange", "fiftyDayAverageChangePercent", "twoHundredDayAverage", "twoHundredDayAverageChange", "twoHundredDayAverageChangePercent", "marketCap", "forwardPE", "priceToBook", "sourceInterval", "exchangeDataDelayedBy", "pageViewGrowthWeekly", "averageAnalystRating", "tradeable", "priceHint", "exchange", "shortName", "longName", "messageBoardId", "exchangeTimezoneName", "exchangeTimezoneShortName", "gmtOffSetMilliseconds", "market", "esgPopulated", "displayName", "symbol"})
in
    #"Expanded quoteResponse.result1"

With the dynamic variable placed in the connection string, the function will now pull stock quote information based upon the symbols we have in our list.

Step 3 – Resolve Connection String Errors

If you clicked done and used this function in your report, everything would be fine inside of Power BI Desktop. However, you are going to run into an issue when you publish to the Power BI Service. Because we are using a dynamic parameter, the cloud service is not sure how to handle authentication. The result is an error in the Power BI Service and a report that will not refresh.’

To resolve this issue, we want to split our connection string to resolve this issue. We will essentially split it into two different sections. The first section will serve as the connection string and help with our authentication. The second half will be treated as a dynamic portion of the query and has no bearing on the authentication process.

In short, all we are going to do is move a portion of that connection string to prevent any errors from happening.

(StockSymbol as text)=>
let
    Source = Json.Document(Web.Contents("https://yfapi.net/v6/finance/", [RelativePath="quote?region=US&lang=en&symbols=" & StockSymbol, Headers=[Accept="application/json", #"X-API-KEY"="bHjSKbiRtr4cOzmOopdrI5TUKX5kMKXU6weUteeL"]])),
    #"Converted to Table" = Table.FromRecords({Source}),
    #"Expanded quoteResponse" = Table.ExpandRecordColumn(#"Converted to Table", "quoteResponse", {"result", "error"}, {"quoteResponse.result", "quoteResponse.error"}),
    #"Expanded quoteResponse.result" = Table.ExpandListColumn(#"Expanded quoteResponse", "quoteResponse.result"),
    #"Expanded quoteResponse.result1" = Table.ExpandRecordColumn(#"Expanded quoteResponse.result", "quoteResponse.result", {"language", "region", "quoteType", "quoteSourceName", "triggerable", "currency", "firstTradeDateMilliseconds", "postMarketChangePercent", "postMarketTime", "postMarketPrice", "postMarketChange", "regularMarketChange", "regularMarketChangePercent", "regularMarketTime", "regularMarketPrice", "regularMarketDayHigh", "regularMarketDayRange", "regularMarketDayLow", "regularMarketVolume", "regularMarketPreviousClose", "bid", "ask", "bidSize", "askSize", "fullExchangeName", "financialCurrency", "regularMarketOpen", "averageDailyVolume3Month", "averageDailyVolume10Day", "fiftyTwoWeekLowChange", "fiftyTwoWeekLowChangePercent", "fiftyTwoWeekRange", "fiftyTwoWeekHighChange", "fiftyTwoWeekHighChangePercent", "fiftyTwoWeekLow", "fiftyTwoWeekHigh", "dividendDate", "marketState", "earningsTimestamp", "earningsTimestampStart", "earningsTimestampEnd", "trailingAnnualDividendRate", "trailingPE", "trailingAnnualDividendYield", "epsTrailingTwelveMonths", "epsForward", "epsCurrentYear", "priceEpsCurrentYear", "sharesOutstanding", "bookValue", "fiftyDayAverage", "fiftyDayAverageChange", "fiftyDayAverageChangePercent", "twoHundredDayAverage", "twoHundredDayAverageChange", "twoHundredDayAverageChangePercent", "marketCap", "forwardPE", "priceToBook", "sourceInterval", "exchangeDataDelayedBy", "pageViewGrowthWeekly", "averageAnalystRating", "tradeable", "priceHint", "exchange", "shortName", "longName", "messageBoardId", "exchangeTimezoneName", "exchangeTimezoneShortName", "gmtOffSetMilliseconds", "market", "esgPopulated", "displayName", "symbol"}, {"language", "region", "quoteType", "quoteSourceName", "triggerable", "currency", "firstTradeDateMilliseconds", "postMarketChangePercent", "postMarketTime", "postMarketPrice", "postMarketChange", "regularMarketChange", "regularMarketChangePercent", "regularMarketTime", "regularMarketPrice", "regularMarketDayHigh", "regularMarketDayRange", "regularMarketDayLow", "regularMarketVolume", "regularMarketPreviousClose", "bid", "ask", "bidSize", "askSize", "fullExchangeName", "financialCurrency", "regularMarketOpen", "averageDailyVolume3Month", "averageDailyVolume10Day", "fiftyTwoWeekLowChange", "fiftyTwoWeekLowChangePercent", "fiftyTwoWeekRange", "fiftyTwoWeekHighChange", "fiftyTwoWeekHighChangePercent", "fiftyTwoWeekLow", "fiftyTwoWeekHigh", "dividendDate", "marketState", "earningsTimestamp", "earningsTimestampStart", "earningsTimestampEnd", "trailingAnnualDividendRate", "trailingPE", "trailingAnnualDividendYield", "epsTrailingTwelveMonths", "epsForward", "epsCurrentYear", "priceEpsCurrentYear", "sharesOutstanding", "bookValue", "fiftyDayAverage", "fiftyDayAverageChange", "fiftyDayAverageChangePercent", "twoHundredDayAverage", "twoHundredDayAverageChange", "twoHundredDayAverageChangePercent", "marketCap", "forwardPE", "priceToBook", "sourceInterval", "exchangeDataDelayedBy", "pageViewGrowthWeekly", "averageAnalystRating", "tradeable", "priceHint", "exchange", "shortName", "longName", "messageBoardId", "exchangeTimezoneName", "exchangeTimezoneShortName", "gmtOffSetMilliseconds", "market", "esgPopulated", "displayName", "symbol"})
in
    #"Expanded quoteResponse.result1"

This is a subtle but important move. By placing the dynamic content inside the relative path, we have eliminated confusion during the authentication process. Power BI will authenticate on the connection string in place and then concatenate the relative path to complete the request. You only need to do this when your queries are dynamic, but it is an important step in the process!

Step 4 – Test the Function

After clicking done, your view in Power Query will have changed. Note that the query list now shows an “fx” symbol for function and you no longer have a tabular list of data. In fact, you have a place to enter a stock symbol. This allows us to quickly test to see if our function is working. Go ahead and enter MSFT and click invoke to see it work.

After you invoke the function, you will be taken to a new query called “Invoked Function” and can see the stock data for Microsoft. That was just to test and see if it works. We can go ahead and delete that query because will not need it again.

Applying the Function

With a working function in hand, it is time to apply it to our data model. I already have a list of stocks in Excel, so I will import that list to Power BI. If your stock list is somewhere else, that is perfectly fine. Just get that list of symbols inside of Power BI.

Once imported, go to your “Add Column” tab and select “Invoke Custom Function”. Select your function from the list. You will notice that the StockSymbol variable will appear. We need to specify which column of values will be passed to that variable. Select the symbol column and click OK.

At this point, you may be prompted about data privacy. If you do, just select ignore privacy levels for now as this is a demonstration.

You should have a new column with the word table highlighted inside of it. We can go ahead and expand those values and confirm the current stock quote info is available for each different symbol.

And just like that you created your own function and applied it in Power Query!

Next Steps

With a working function, what is left to discuss? As I stated at the beginning of this series – each API is like a snowflake. They all are unique and have their own challenges. This is a single example of how to connect a REST API to Power BI. There are challenges and other considerations you must balance when creating your reports. In my next post, I will dive into challenges you will see when leveraging other APIs inside of Power BI.

Until then, was this your first time creating a function? Did you find it challenging? Do you have other applications for a function inside of Power BI? Tell me in the comments below!

In my last article, I discussed the basics around REST APIs. We did not do anything with Power BI. While I did not get to the real purpose of this series, it was important to establish the basics. Using the elements we discussed, you can copy and paste them into Power BI to connect to your API.

For this post, I am using the Yahoo Finance API to demonstrate how this works. I do not receive any kick back for sharing this API. They have a free tier and it is a great API to use for beginners. If you want to try this on your own, you can follow along with this article.

RTFM – Read the Fine Manual

Before you do anything with APIs you must review the documentation. I worked with an API a few years ago that required a unique API key for each individual endpoint. If I had spent some time reviewing the documentation, I would have prevented hours of frustration as I tried to connect to various endpoints. If you are like me, you might find this frustrating. However, I find reading the documentation far less frustrating than constantly struggling to get an endpoint to work inside of Power BI.

Identifying Usable Endpoints

The first time I review documentation I am sorting out which endpoints are useable or not. I need to find out which API endpoints that will work with Power BI. I opened the documentation and was excited about what I saw…

At a quick glace, all of the endpoints are using the GET connection method. As a result that means every single endpoint can be used in Power BI. That is great to see!

Which Endpoint is for Me?

Knowing what you are looking for is key when reviewing documentation. I want to find stock price information and compare prices. Quality documentation will have one of two things to help you with this process:

• A data dictionary that clearly defines each column in the query
• A same response from the query

This documentation brings back a sample. As expected, I can find which endpoint meets my needs. As an example, I am interested in stock prices. According to the documentation, I can use the quote endpoint to accomplish my goal.

Setting the Parameters

Now that we have the connection method and endpoint, we need to establish what parameters are needed. Sometimes parameters are identified but not clearly documented. As a result, you might get frustrated because you cannot apply parameters to your query. This API is much easier to understand because of the clearly labeled parameters with sample inputs.

As you can see, the documentation provides sample values for each parameter so you know how to leverage it. This results in far less frustration because you know what values are accepted for each parameter.

Since this API has an option to try it out, I have updated the parameters to pull back Microsoft’s stock information. This allowed me to validate if my parameters were correct and saved me a ton of headaches. Since it worked, you can see that it came back with a response.

As a result of the test, there was another valuable bonus. The documentation assembled my connection string by putting the endpoint url and parameters together into a single connection string. How convenient!

Header Information

Up to this point the Yahoo Finance API documentation has explicitly called out each of the REST API elements. However, the headers in this endpoint are not as easily identified. We have to dig a little deeper to find them.

You probably missed the box above the connection string labeled Curl. Curl is a library used to call APIs if you are developing an application. While we are not developing an application, this box does help us identify our headers. If you notice, there are two lines with “-H” at the beginning. These are the header values we have been looking for!

Double Check

At this stage, we have identified all the elements we need for our connection in Power BI. We have the connection method, endpoint url, parameters, and headers. Remember that we are not using a POST connection method, so we do not need a body for this request. Now we just need to plug it into Power BI!

Connecting to our REST API (Finally!)

With all of our elements in hand, we can open up Power BI and start building our connection to the API.

Step 1 – Select the Web Connector

Open Power BI, select “Get Data”, and choose the Web connector:

Step 2 – Copy/Paste Elements into Power BI

First things first – switch to the advanced mode for the Web Connector so you can add all of the required details.

You will notice that there is no option to select your connection method in this view. Power BI defaults this to GET, so you do not need to configure anything. One less thing to worry about!

Go back to the documentation and copy your connection string. If your documentation does not assemble this for you, you might need to do this by hand. Once assembled, paste it into the URL Parts box in the web connector.

Next, we can add the headers. This endpoint has two – Accept and X-API-KEY. You will only see one set of boxes at the bottom. You can simply click “Add header” to accommodate for the second header.

For the Accept header, we can select it from the drop down on the left as it is a commonly used header. On the right, copy and paste the value found in the API documentation.

For the X-API-KEY header, you can enter your own value in the drop down or copy/paste it from your documentation. You can copy your API key from the documentation as well into the box on the right.

By bridging the documentation with the web connector, we have successfully filled in all of the blanks for the connection method, endpoint url, parameters, and headers. With everything in place, we can click okay and connect!

Step 3 – Authentication

Since this is the first time we are using this connection, we are prompted to select an authentication method. If you are using the Yahoo Finance API, you can easily select Anonymous and click connect as our API key handles our authentication.

On the left, you can see there are other authentication methods. Sometimes your connection method will require a username and password. I have experienced this with ServiceNow and Honeywell APIs. If you are adventurous and want to try using the Microsoft Graph API, you will need to use your organizational account. You will need to review your documentation to determine if you need to use other forms of authentication to use an endpoint.

Transformation Time

By following these steps, you should now see your stock data inside of Power Query. All of the information you saw in the sample response should be in a tabular format and ready to go. For an easier view, I made some adjustments so you could easily compare the values:

With this query in place, you can quickly refresh the data and will always have up to date stock quote information for Microsoft.

Next Steps

With everything connected, you probably think we are finished. If there was only one stock we cared about, we would be in good shape. However, investors are looking at several different stocks each and every day and this query only pulled one. In my next article, I will show you how to scale this query so whether you have 10 or 1,000, you will have a maintenance free report that always refreshes.

Until then, did you follow along with the Yahoo Finance API? Were you able to get some valid data? Tell me in the comments below!

We have all been there once before. We are using a 3rd party tool and we want to extract data from it. You might have an option to export the data to a CSV or Excel file, but that requires you to be involved and can result in errors.

Next you might reach out to the support team and they send back documentation for their APIs. They think you are a programmer and probably know how to use them. But in a world full of citizen developers not everyone knows how to use these APIs to bring data into Power BI.

This series aims to demystify the process and start getting that data into Power BI and eliminate those data exports. And believe it or not, it will require a minimal amount of code to make it happen!

What is REST?

REST APIs (also known as RESTful APIs) is a specific architecture of an Application Program Interface (API). Known as the Representational State Transfer (REST), it has a standard set of rules that are widely used in the programming world. It scales well and has become a commonly accepted API that is stable. REST APIs fill a specific need to simplify integration of data between different applications.

API requests are fairly straight forward. It starts with a request from you (the client) to an API endpoint. After being authenticated, the request continues on to a database with the data you need. That data is returned back to the endpoint where it is formatted and then passed back to the client.

For many, this flow makes a ton of sense. However, if you are not from a programming background, this can be a little intimidating. When you read API documentation, it is often full of code snippets and it can be difficult for you to get started. Sorting through these snippets and figuring out how they work can be complicated and time consuming.

But here is the good news – Power BI can handle these API requests often with no code required! The trick is understanding how REST APIs are structured and then plugging the information from the documentation into the right place.

Anatomy of REST APIs

So if we can take the documentation and plug it into Power BI, it is important to understand how REST APIs are constructed. Once we understand the anatomy of an API, it becomes easier to connect via Power BI. There are five common elements that are leveraged with REST APIs:

• Method
• Endpoint URL
• Parameters
• Headers
• Body

You will always need a Method and Endpoint URL when using REST. However, the other elements will vary based off of the documentation. You will have to read your documentation carefully to make sure you have everything you need.

To better understand these elements, let’s take a look at them individually to understand what they do and how they work.

Method

There are four methods that are used with REST APIs: Get, Post, Put, and Delete. Methods help instruct what is happening when the API is called. For example, if you called a Delete method, you would be deleting content on the server.

To make our lives easier, the Get method is the most common one we will use and is the easiest to implement. Post can be used sometimes, but it requires a little more effort and coding in Power Query to make it work. You will never use Put or Delete in Power BI.

Endpoint URL

The Endpoint URL determines which specific API we are calling. There will be multiple APIs available, so it is important to determine which one you need. In reviewing your documentation, you should be able to determine which endpoint contains the data you need to query.

Parameters

Parameters filter the results of your request. Notice the “?” that separates the connection string. Before it is the Endpoint URL while after are the parameters. Multiple parameters are separated by ampersands (&) and strung together.

Parameters speed up requests as they reduce the amount of data requested. Often optional, but sometimes required. The API documentation will specify if any parameters are required.

Headers

Headers are designed to pass information about your request. The most common header you will need is an API key or token but you may run into others. Another common header you might need to identify is the Content-Type to specify how we want to see our response.

Body

Since we are using the Get method primarily in Power BI, you will not need the body. However, it is worth mentioning it in case you use a Post method in the future. The body is another set of parameters to assist with the request.

Documentation is your friend

If you are like me then you hate reading directions. I love working through things on my own and discovering. But after many lost hours, I have learned to take a few minutes to read the documentation that comes with an API first. It takes time, but there are several reasons to take a few minutes and understand how the API functions.

Reason #1 – Each API is like a snowflake

Every API is unique and has their own requirements. You will find some that require certain parameters to be declared. Others might need a token. I even worked with one that required a different API key for each endpoint! Understanding the components of our API will reduce headaches as we go to use them.

Reason #2 – Ensure you are receiving the right data

The best documentation is paired with a dictionary to help identify the data being returned. You may need two or three APIs to get all the information you need. Taking a few minutes to understand what data is available will help you build a plan as you build your connections.

Reason #3 – Try it out

Often APIs have an option to try them out. You can select an endpoint, fill out the parameters, and then submit the request. It brings back a sample of the data and even will assemble the connection string and headers for you. It also helps identify any required parameters and diagnose issues before you move into Power BI.

Next Steps

Now that we understand the basics around REST APIs, the next step is to transfer what we have learned into Power BI. You might be wondering why I took the time to understand the basics of REST APIs. As I mentioned before, many of these APIs can be used with no code. With a strong understanding of how they are built, we can copy/paste these elements into Power BI and start querying data. In my next post, I will show you how to connect to the Yahoo Finance API to query stock quotes in real time.

Until then, have you used any APIs in Power BI? Do you have any favorites that you like to use? Tell me in the comments below!