I’ve done a fair amount of research around dynamic and parameterized queries, specifically around an Excel query parameter, as in trying to pass a parameter to a SQL query in Power Query. After much trial and error, I finally have found a solution that works. Here’s the quick and easy way to do this and harness the power of query folding. This solution works in Excel – the process is a bit different in Power BI.
Please note that this post assumes you are at least moderately familiar with Power Query and SQL querying. Your mileage may vary depending on your situation.
In my example, “SParameter” is the name of the parameter I am using, and it represents a store number (retail location identifier). The related field in my SQL table is [Store].
Create the parameter:
- Add a table, with a single record and column. This can be on any tab in your workbook.
- Add this table into Power Query by selecting the table, then Data > From Table/Range. When the query editor opens, if necessary, change the data type (in my case I need it to be text).
- Right click on the record and select “Drill Down”. Since you have only a single record, this step will automatically create a parameter.
- In the properties, I name this SParameter (you may enter the name of your choice for your parameter). Note that the name is case sensitive.
Create the SQL query:
Build your SQL query as normal, but note that we are not going to put a where clause in referencing the new parameter here (see “Why Not Include the Parameter in the SQL Statement” section below). Here’s my simple query example – notice that I’m not including the store field in the criteria section of the query though this is the field my parameter will ultimately filter on.
Select * FROM Storelist WHERE OpenDate < GetDate()-365
If you think like me, you may be pausing here – my table has millions of records and I don’t want them all pulling in – don’t worry, this is the beauty of the process.
- Write your SQL statement in Power Query as noted above.
- When the Query Editor returns the columns and record sampling, for the field you will be using your parameter, filter with any single value (Text Filters > Equals). This is simply a placeholder, to create the Power Query M formula for the next step.
- You will now see that filtering in the formula bar.
- Replace the placeholder value with the name of your parameter, removing any quotes from the placeholder. This is how it looks for me: = Table.SelectRows(Source, each [Store] = SParameter).
- Power Query is smart enough to modify its native query to use the parameter, so it’s not going to pull in the millions of records and then filter after the fact. Success!! This is the power of Query Folding!
- Side note – if you are wondering about GetDate(), this is the SQL current system date, so in a way this is technically a dynamic parameter as well. In my case, the query will only return stores with an open date that is older than 365 days based on today’s date. You may find this useful for your query as well.
Why Not Include the Parameter in the SQL Statement?
In the SQL statement, logic would lead us to add the store number/SParameter as part of the criteria in the select statement. It may seem counter intuitive, but we cannot successfully put the parameter directly into the SQL code/query. I have tried several times, but the challenge is that you are combining data sources and at this time, this is not allowed due to the built in security (SParameter portion is local, SQL portion is external).
If you are tempted to test this yourself, the format would be Select * FROM Storelist WHERE Open < GetDate()-365 and Store = “&SParameter&”. You will likely run into this error “Formula.Firewall: Query ‘SParameter (2)’ (step ‘Filtered Rows’) references other queries or steps, so it may not directly access a data source. Please rebuild this data combination.”
I truly hope this post helped you out. If so, please feel free to leave a comment below letting me know so, and if you’d like, add what you’d like me to cover in a future post. Also, feel free to share this with someone else who may find it useful.
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