Forum Discussion
Restrict rows retrieved by query?
The single-qoutes is needed as part of my SQL query to filter a string column in the SQL database
The 1st double-qoute stop the "free text query" and allows to insert a parameter
Ampersand is needed to merge the parameter with the SQL code around paramater
The 2nd double-qoute continue the "free text query"
I hope this explains the code.
Now back to your problem... 19 foreign keys "scary face". I assume that you users will need to be able to filter several parameters at once? This will force you to type SQL code from now until you retire. As I see it you will have to create 19*18*17*16*15*14*13*12*11*10*9*8*7*6*5*4*3*2 combinations of your code + create 19 parameters lists with a complete set of values for your user - and this will only give them the option to select a single value per parameter. I don't think this is the right path for you. You will need to many different variations of your code because consider that your user only select a parameter in a few of your lists, then the rest will be blank but if you query your SQL with WHERE a.Country = '' then you will only get the customer with no country value (blank), but what you really want is not to filter the country column in your SQL table, so you will somehow have to handle all the combinations of posible where clauses you need.
With single value per parameter I mean they will not be able to select both US and UK customers but only one of them - unless you make you parameters free text values. Then you will be able to chance the SQL to use IN instead of =, but your users will only get the wanted result if they learn to write the right text - using my example from before this would be 'US', 'UK' and your where clause should be "WHERE a.Country IN (" & CountryParameter & ")"
Qiuyun_Yu,
Thanks for your feedback. The first of the links you gave was informative and I hadn't seen it before.
The problem I'm having is trying to relate the query parameters to the SQL Server select statement. As the link shows, it is possible to change the values used for a data source. And there are some good blogs that show how to change the SQL Server instance that the query connects to, for example. But I cannot find a simple way to modify the SQL query so that it incorporates the query parameters, without learning the new language and creating very specific code in the Advanced Editor to use it.
I'm new to Power BI, so please correct me if I'm wrong, but the problem I see with using filter conditions is that SQL Server will still return all of the universe of rows it contains, and the filter will be applied when it is displayed or used in a visualization or report. I do not want SQL Server to return 123 million rows so that the user can filter down to the one thousand or so rows he/she is interested in. Instead, the user should be able to enter values for the parameters, which are then sent to SQL Server as part of the query, and it returns just the one thousand rows of interest.
Is this possible? I haven't found a way to do it, but I sure would like to - without advanced coding, something our users can set up and do. Each user will have specific columns of data they are interested in seeing from the operational data store, and specific criteria to use to select the rows they are interested in. And the number of such requests is huge - far more than our staff can develop for each user. Essentially, we would like Power BI to be an end-user ad hoc tool for operational data as well as for aggregated data from sources like SSAS. And I'm not seeing a way to do it.
Thanks for yoru help.
SamTrexler - it will be possible to implement these parameters in the SQL Query - I do it in a "content pack" I have created for our customers using Microsoft Dynamics NAV. The problem with creating a dynamic model for Dynamics NAV is that the tables, where the data is stores, is prefixed with their company name so table names is always different from customer to customer.
So what I did was creating a file with 3 free text parameters Server, Database and Company and I pass all 3 parameters on to the queryes against the source SQL database.
As I read the thread free text paramaters will not cut it for you and there is some limitations that you need to be able to fullfill if this is the right way for you to go.
1. You need to be able to create full parameter lists with all the values your users would want to filter on.
2. It will satisfy your users need only to be able to select on value for any of your parameter lists.
2. I don't think it will work for you if your users will need to be able to filter on a lot of different columns in your solution
3. You need to be able to write the query so it can handle that your users only filter perhaps 1 out of x parameters in your model.
Basically you will have to write one SQL statement that can handle all the mixes of parameter selections made by the user. The user however is limited to only being able to select the values of the parameters provided by you and from reading your previous posts this just seems to be to simple compared to what you want?
However if you want to test this I will give you an example of how you can use parameters in your SQL query.
In this example I wish to return all the customers from my customer table where country is US - the country is what my user selected from a parameter list containing all the possible countries in my table. In this example I have called my parameters list CountryParameter
let
Source = Sql.Database(Server, Database, [Query="
--SQL Query Start
SELECT
a.DWID_Customer AS 'CustomerKey'
, a.CustomerNo AS 'Customer No.'
, a.Name AS 'Customer Name'
, a.CustomerLabel AS 'Customer'
, a.CustomerPostingGroup AS 'Cust Post. Group'
, a.Country AS 'Country'
, a.City + ', ' + a.Country AS 'City'
FROM D_Customer a
WHERE a.Country = '" & CountryParameter & "'"
--SQL Query End
"])
in
SourceI hope it makes sence I am a bit tired.. he he
sdjensen, that got me the solution I needed. Thanks so much, I'll Accept your answer.
I actually took a slightly different tack in the end. Instead of modifying the WHERE clause in the Advanced Editor, I created a filter on each column that referred to the parameter. So for a range of dates against a DateTime column in the database I created two parameters with type "any" and entered the formula
= Table.SelectRows(#"Reordered Columns", each [KeyDateTime] >= DateTimeZone.From(StartDate) and [KeyDateTime] <= DateTimeZone.From(EndDate))
and for a number column in the database that can contain nulls, I created a parameter with type "Text" and entered the formula
= Table.SelectRows(#"Filtered Rows2", each (Text.From([InspMethod]) = InspMethod) or (InspMethod = "ALL") or (([InspMethod] = null) and (InspMethod = "BLANK")))
So that the user can enter "ALL" to retrieve all rows including nulls, "BLANK" to retrieve rows with null, or a value to retrieve rows with that value.
The advantage of this approach is that I only need a generic query, not 19*18*17... queries or a complex one that tests for the presence of parameters, or all 19 parameters in every query with a convoluteted WHERE clause, etc. It appears that the query gets generated with the parameters it needs.
It seems to be working great.
Thanks for the lead and great information.
Regards,
Sam
sdjensen, thanks for the example. I'll give it a try. Just to make sure I'm reading it right, the parameter should be specified as: <single-quote><double-quote><space><ampersand><space><parameter I created in Power BI><space><ampersand><space><double-quote><single-quote>?
So far, we've identified 19 foreign keys that will probably becomes dimensions in our data warehouse - and are probably fields users will want to select on. Right now I'm working with a subset - two dates and three text fields. If I can get those to work and be optional, I'll see about sharing the query, letting it retrieve all columns (the user can hide columns they don't need.) That might be workable.
Thanks for the suggestion. I'll reply again with the results.
The single-qoutes is needed as part of my SQL query to filter a string column in the SQL database
The 1st double-qoute stop the "free text query" and allows to insert a parameter
Ampersand is needed to merge the parameter with the SQL code around paramater
The 2nd double-qoute continue the "free text query"
I hope this explains the code.
Now back to your problem... 19 foreign keys "scary face". I assume that you users will need to be able to filter several parameters at once? This will force you to type SQL code from now until you retire. As I see it you will have to create 19*18*17*16*15*14*13*12*11*10*9*8*7*6*5*4*3*2 combinations of your code + create 19 parameters lists with a complete set of values for your user - and this will only give them the option to select a single value per parameter. I don't think this is the right path for you. You will need to many different variations of your code because consider that your user only select a parameter in a few of your lists, then the rest will be blank but if you query your SQL with WHERE a.Country = '' then you will only get the customer with no country value (blank), but what you really want is not to filter the country column in your SQL table, so you will somehow have to handle all the combinations of posible where clauses you need.
With single value per parameter I mean they will not be able to select both US and UK customers but only one of them - unless you make you parameters free text values. Then you will be able to chance the SQL to use IN instead of =, but your users will only get the wanted result if they learn to write the right text - using my example from before this would be 'US', 'UK' and your where clause should be "WHERE a.Country IN (" & CountryParameter & ")"
sdjensen, thanks for the explanation.
And you're exacty right about the combinations of parameters, that's what worries me and what I meant by making them "optional". If I can find a way to make the WHERE clause ignore a parameter if it's null or if it has a certain value (like "ALL"), without sending performance down the drain, then I can create a single query for everyone to use. Otherwise this will be prohibitive.
Not matching on an empty parameter value is the same problem I have when I try to use Microsoft Query in Excel (which allows me to link a query parameter to a cell on the spreadsheet.) I'm hoping that with the capabilities of Power BI I can get around it.
Thanks again,
Sam