Relationships on columns with non-unique values and how to tune them | Gerhard Brueckl's BI Blog
You can encounter Pitfall #10 whenever you create lookup tables in Power BI. steps that are crucial to ensure that your report won't fail to refresh. . on the relationship side, Power BI (and the implicit Power Pivot engine) is case can exclude the lookup table from the refresh sequence, by un-checking. I started checking in on SQLRockstar's blog a bit more. The metadata columns that describe the date can contain duplicate values. We can use a calendar table in Power Pivot to create a relationship between . What's up,I check your blogs named “The Calendar Table (Date.
This is a list of common use cases. Profit and Loss Account Hierarchy Most profit and loss statements have a native parent-child hierarchy for representing the list of accounts.
When this is not the native representation in the data source, a parent-child hierarchy can be useful to show an alternative custom grouping of original accounts, such as in balance sheet reclassification. Bill of Materials A list of components of a product is usually a native parent-child hierarchy, because each component has other subcomponents, with different levels of depth in different branches of the hierarchy. Calculations related to measures in a bill of materials are described in another dedicated pattern, Bills of Materials.
Organizational Structure Company organizational structures are often represented as parent-child hierarchies. One of the limitations of parent-child hierarchies is that each node must have a single parent.
Complex organizations that do not respect this constraint require more complex graphs, and mapping them to a parent-child hierarchy requires a normalization to a regular organization tree.
Complete Pattern Suppose you have a Nodes table containing one row per node, with a ParentKey column that defines the parent of every node.
The Transactions table has a many-to-one relationship with the Nodes table. You can see the two tables in Figure 7. You create a hidden HierarchyPath column containing the result of the PATH function, which provides a string with the complete path to reach the node in the current row of the table, as shown in Figure 8. You naturalize the hierarchy by creating a hidden column for each level of the hierarchy. You have to define the maximum depth of the hierarchy in advance, planning enough levels for future growth.
For each level, you populate the column with the node name of the hierarchy path at that level. Figure 9 The HierarchyDepth column defines the level of the node in the current row. This model creates the following report. You can see this model with this report in the Duplicated Demo At this point, you can break the calculation made in Net Margin by importing a column called Margin in the table Countries.
This can be done in many ways: In our example, we use this latter technique, modifying the definition of the table Countries using the following DAX code. The content of the report is now completely different.
As you see in the previous screenshot, the Net Margin measure produces completely different numbers, because its calculation no longer works as expected. We can fix the report by modifying the definition of the Net Margin measure using a measure reference that also includes the Customers table name, as in the following example.
This will restore the original calculation. The formula editor in Power BI highlights the Margin name with a purple color, so you can recognize that it is a measure reference instead of a column reference. This way, you should be able to avoid the confusion between column reference and measure reference regardless of the presence or absence of the table name.
Duplicated names in DAX - SQLBI
However, this is not a perfect solution, because the code highlighting is not always clear and not always available in other editors. Power BI does not allow you to create a column if a measure with the same name already exists within the same table.
Thus, trying to add a Margin column in the table Customers is not possible, unless you remove or rename the existing Margin measure first. DAX code generators Considering the behavior of the DAX syntax, it is inevitable that a DAX code generator uses an explicit table name in any measure reference, just because this way the code obtained is more resilient to column names conflicting with existing measure names.
As a data modeler, you should be aware of the existing names, and adopt a naming convention that should avoid confusing a column name with a measure name. For example, if [Revenues] could be a good name for a measure, the underlying column that is aggregated should have a different name. There are too many scenarios to consider, and what is important is being consistent with a set of rules.
You need to define one, especially if your model grows and is modified and maintained by different people. You can use formulae in your columns to calculate the values for Year, Month etc. Also note that you will generally be better off to create a new workbook for your calendar and save it somewhere you can easily find it later.
This has 2 benefits.
Power Pivot Calendar Tables
Firstly you only have to create the date table once use many times and secondly it is best practice to not use linked tables in your workbooks there are exceptions. If you use a linked table, the data is first stored uncompressed in your workbook, and then stored again in a compressed format in your data model.
An alternative approach to Excel is to use Power Query. Some DAX measures like YTD have a problem where the data in your data table will end before the dates in your calendar table end.
- Relationships on columns with non-unique values and how to tune them
- Recent Posts
- The Calendar Table (Date Dimension) Explained for Power Pivot & Power BI
The easiest way to solve date over run is to only load dates in your calendar table up to and including the last date in your data table. Power Query is not only a great tool for creating calendar tables, but it is also very easy to solve the date over run problem.
A mystifying and awesome solution for many 2 many - PowerPivotPro
I have written a number of blogs on how to use Power Query to create calendar tables and these blog posts include detailed instructions on how to do it. Here is the most recent blog article. If you want a comprehensive lesson on how to use Power Query, checkout my training course here https: