In Power BI, I am attempting to join a dimension table with a fact table. The dimension table has approximately 1.1M rows in it (a lot I know for a dimension table). All the values are unique. When I attempt to join this to the fact table, PBI automatically creates a M:M relationship. When I attempt to change this to a 1:M, I get a message saying "The cardinality you selected for this relationship isn't valid".
Here is the query that generates the dataset. As you can see, it's impossible for there to be duplicates.
SELECT DISTINCT
[TranDesc] as TransactionDescription
FROM [dbo].[dGLTranDescription];
Why would I get this message?
Try to validate that Power BI seeing values in the dimension table as unique. Depending on your data, source system and PowerBI may see it differently.
Here are suggestions from https://community.powerbi.com/t5/Desktop/The-cardinality-you-selected-isn-t-valid-for-this-relationship/td-p/73470
1.
Create two measures to verify in Power BI:
TotalRows = COUNTROWS('DimTableHere')
DistinctRows = DISTINCTCOUNT('DimTableHere'[DimTableJoinColumnHere])
After create those two measures, place them in two card visuals, if
results are different, it means there are duplicate values in your
Dimension table.
2.
If you had duplicates when first creating relationship and now you don't, deleting the relationship and recreating it may resolve it.
If you have removed duplicates on the relationship column and it still considers it as invalid cardinality, try running Text.Clean on that column prior to duplication removal. I've had a special character but the removal of duplicates on the query, the values counted as different there but once imported they were considered the same.
Related
I have a data base with the following tables:
Customers, Invoices, Salesman, Target.
The ones concerned about my question are Customers, Invoices.
There are customersIDs used in the Invoices but doesn't exist in the Customers table.
If I used only the customers from Customers Table, my customer dimension would be incomplete.
My solution is to append these IDs from Invoices to Customers and fill other columns in the Customers table with nulls.
I don't know if this is the best approche according to Kimball?
also, if it is a good solution, how can I add accomplish it with Power bi desktop?
Customers table: "generated Data"
Invoice table:
..... just a sample the table is thousands of rows.
There's two points here:
Firstly, (in import mode at least) PBI already creates the "blank row" for items present in your fact table but missing from your dimension table for precisely this scenario. If you don't need the granularity of each individual missing customer id, then you don't need to do anything.
Secondly, if you need to to retain that granularity then your approach is the correct one. The way to do this in Power Query is as follows:
Create a new query which takes your customer dimension table and does a left outer join on customer id with your invoice fact table.
Expand the newly joined table but retain only the new customer id column.
Remove all columns apart from the new customer id column.
Remove duplicates
You now have a list of missing customer ids. Ensure the column name is the same as the column name of you customer id in the customer dimension table. Append this to the original customer dimension query and the nulls will be filled in automatically for the missing columns.
Please keep in mind that It is Kimball, not Kimble.
There are 4 steps of DWH Methodology:
1) Understand Business Process (What your process is actually measuring?)
2) Deciding the grain (It means what every row in your fact table actually represents?)
3) Deciding Dimensions (Ask Where-What-Who-Where-How-HowMany-HowMuch to your grain declaration formed together with business processing)
4) Define Facts (Metrics)
According to this order, You define Dimension tables before building your fact tables: If your dimension table , Customer table in this case, is missing in terms of customers available in your fact table, My biggest biggest advice according to the DWH Dimensional Modeling is to set your customer table right!!! Define every piece of customer in your dimension table!!!! Then populate your Fact table with records:
[Customer ID] in Customer Table : PRIMARY KEY
[CustomerID] in Invoice Table : FOREIGN KEY
SQL and Power BI reacts very differently in your problem:
1) Power BI has no referential integrity concept: It adds a blank row to your dimension table in such a case.
2) SQL gives referential integrity error, and you can't even add rows to your fact table. I support SQL in this case personally!!!!
Finally: Use some ETL tool(SSIS, Talend, ODI or even Power Query) to make your dimension table as accurate as possible:
For example:
Do not leave any column value as null!
If an unknown date exists, put a default date value like '1900-12-31'
If an unknown textual property, put in keywords 'unknown','not available' etc..
Because dimensional table are sources of querying in SQL statements; and different SQL Vendors (SQL Server, Oracle, MySQL) has to deal with NULL values in a different way, and this cause problems in terms of performance wise!!
I have to divide two measures from two different tables. I have created a measure in Table A & created measure-2 in Table B.
When I use matrix visual in Power BI by taking date field in columns and region in rows (for table A&B), I can see the both table values are correct as I am expected.
Ex: Table A 2017-Q1 value by measure1 is 29.2, Table B 2017-Q1 value by measure1 is 2.9.
I have to divide both measures and I need to show the value (divide%) in TableA along with Measure1.
Unfortunately I tried in multiple ways by forming relationship b/w two tables also, But not getting the expected result i.e., 29.2/2.9 we should get 10% but instead of that getting 3%.
Without knowing your data model, it's hard to give a reasonable answer.
https://learn.microsoft.com/en-us/dax/related-function-dax
Your best change of understanding what happens is to learn up on relations, and changes them when needed. The documentation is a great starting point.
Unrelated data plotted in a visual of different data will always aggregate since there is no relation to split your values. The value of 3% is correct, your assumption that you want 10% as an outcome is not valid for your situation.
If you link the dates of table A and the dates of table B to a seperate Calendar, it all would work.
In my table primary key column have missing value, i have tried to fill using measure but it is not work because not full fill the primary key val of column to measure
For handling missing values, you need to follow the following two steps:
Replace the missing values with the desired values in Query Editor in Power BI Desktop (optional)
Remove the bi-directional relationships and create uni-directional relationships among tables
Note: The direction of the relationship plays a very important role in modeling in Power BI. The direction of the relationship means the way that filter propagates in Power BI. The uni-directional relationship will filter one table based on the other one. Sometimes you need to filter in a different direction, that is when the bi-directional relationship comes into play. However, bidirectional relationship comes with a cost of performance issues. Do not use bi-directional relationships blindly. Make sure you have designed your model in the right way first, and if that doesn’t work, then try other methods such as Cross-Filter DAX functions.
I have created static table as blow and create relationship with original tables then assigned value static table column on visual table which is working with out any issue
Create Static stable:
create relationship
assign column to visual table and filter result column should not be empty
I have two tables from Azure SQL in PowerBI, using direct query:
EMP(empID PK)
contactInfo(contactID PK, empID FK, contactDetail)
which have an obvious one-to-many relationship from EMP.empID to contactInfo.empID. The foreign key constraint is successfully enforced.
However I can only create a many-to-one relationship (contactInfo.empID to EMP.empID) in PowerBI. If I ever try the opposite, PowerBI always automatically converts the relationship to many-to-one (by swapping the from and to column), which prevents me from creating visuals. Does PowerBI think the two are equivalent?
Update:
What I'm doing is to just create a table in PowerBI showing the join results of these two tables. The foreign key constraint is contactInfo.empID REFERENCES EMP.empID, which is many-to-one. That should not be a problem, I guess, since I can directly query the join using SQL.
Please also suggest if I should create the foreign key in the opposite direction.
More info on failure to create visual
The exact error message is:
Can't display the data because Power BI can't determine
the relationship between two or more fields.
Version: 2.43.4647.541 (PBIDesktop)
To reproduce the error:
DB schema is as follows:
What I want is a table in PowerBI showing contact and sales info of am employee, that is, joining all the four tables. The error will occur when VALUES of the table visual contains "empName, contactDetail, contactType, productName", however, error will NOT occur if I only include "empName, contactDetail, contactType" or "empName, productName". At first I thought the problem may lie in the relationship between contactInfo and emp, but it now seems to be more complicated. I guess it may be caused by multiple one-to-many relationships?
Expanding my comments to make an answer:
Root of the Problem
In your data model, a single employee can have multiple contacts and multiple sales. But, there's no way for Power BI to know which contactDetail corresponds to which productName, or vice versa (which it needs to know to display them together in a table).
Deeper Explanation
Let's say you have 1 emp row, that joins to 10 rows in the sales table, and 13 rows in the contactInfo table. In SQL, if you start from the emp row and outer join to the other 2 tables, you'll get back (1*10)*(1*13) rows (130 rows in total). Each row in the contactInfo table is repeated for each row in the sales table.
That repetition can be a problem if you do something like sum the sales and don't realize a single sales record is repeated 13 times but might be fine otherwise (e.g. if you just want a list of sales and all associated contacts).
Power BI vs. SQL
Power BI works slightly differently. Power BI is designed primarily to aggregate numbers, and then break them down by different attributes. E.g. sales by product. Sales by contact. Sales by day. In order to do this, Power BI needs to know 100% how to divide numbers up between the attributes on your table.
At this point, I'll note that your database diagram doesn't include any obvious metrics that you'd use Power BI to aggregate. However, Power BI doesn't know that. It behaves the same whether you have metrics to aggregate or not. (And failing all else, Power BI can always count your rows to make a metric.)
Let's say that you have a metric on your sales table called Amt Sold. If you bring in the empName, productName, and Amt Sold columns, Power BI will know exactly how to divide up Amt Sold between empName and ProductName. There's no problem.
Now add in contactDetail. Using your database diagram, Power BI has no way of knowing how an Amt Sold metric in the sales table relates to a given contactDetail. It might know that $100 belongs to empID 27. And that empID 27 corresponds to 3 records in the contactInfo table. But it has no way of knowing how to divide up the $100 between those 3 contacts.
In SQL, what you'd get is 3 contacts, each showing the $100 amount sold. But in Power BI, that would imply $300 was sold, which isn't the case. Even equally dividing the $100 up would be misleading. What if the $100 belonged entirely to 1 contact? So instead, Power BI shows the error you're seeing.
My Recommendations
If you can, I recommend changing your data model before your bring it in. Power BI works best with a single fact table, which would contain your metrics (like amount sold). You then join this fact table to as many lookup tables as you like (e.g. customer, product, etc.), directly. This allows you to slice & dice your metrics with any combination of attributes from any of the lookup tables. I would recommend checking out the star schema data model and the concept of lookup tables: powerpivotpro.com/2016/02/data-modeling-power-pivot-power-bi
At the very least, you would want to flatten your tables (i.e. merge the contactInfo and sales tables into a single table before importing them into your data model.
It may be that Power BI isn't the best tool for what you're trying to accomplish. If all you want is a table showing all sales & contact info for an employee, without any associated metrics, a regular reporting tool + SQL query might be a better way to go.
Side Note: You can't reverse a many:one relationship to get past this error. The emp table contains one row per empID. Both the contactInfo and sales tables contain multiple rows with the same empID. This means the emp table is necessarily the "one" side of the relationship to both those tables. You can't arbitrarily change that.
I'm attempting to create a shared date dimensions between two fact tables in Power BI, based off of a relational data source.
Currently, if I include an unrelated dimension in the report, I get numbers duplicated across multiple rows, where they don't really apply.
I'm wondering if there is any way to tell Power BI that certain dimensions cannot be used with certain fact tables, similar to using IgnoreUnrelatedDimensions in SSAS.
Currently the only solution I can find is to create a separate date dimension, so that the two fact tables have no relationship that could be used to join them, however this would mean forfeiting the ability to do any time based comparisons.
Create a combined view of the fact tables with only compatible columns to be used for time based comparison:
In Query Editor, create new queries for your fact tables by
referencing i.e. right click original query and select "Reference".
Then in those "copies" cut out the incompatible dimensions.
Rename columns to align terminology (e.g. Sales Date ==> Transaction Date, Payment Date ==> Transaction Date).
Use "Merge Queries" function to combine the copies using Full Outer Join.
Join this merged view to your date dimension