Daily DAX: Day 78 INFO.FORMATSTRINGDEFINITIONS
The function INFO.FORMATSTRINGDEFINITIONS in Power BI corresponds to the TMSCHEMA_FORMAT_STRING_DEFINITIONS Dynamic Management View (DMV) in the context of Power BI's model metadata. Here's a detailed explanation based on the search results:
Overview of INFO.FORMATSTRINGDEFINITIONS
Function: INFO.FORMATSTRINGDEFINITIONS([<RestrictionName>, <RestrictionValue>, ...])
Returns: An entire table or a table with one or more columns, specifically corresponding to the TMSCHEMA_FORMAT_STRING_DEFINITIONS DMV.
Main Use Case:
Metadata Querying: The function is used to retrieve detailed information about format string definitions within the Power BI model. This includes how data formats like currency, dates, or custom formats are defined and used within measures, calculated columns, or other model objects.
Model Documentation: This function can be particularly useful for documenting the Power BI model. It helps in understanding how data formatting is applied throughout the model, which is crucial for maintaining, auditing, or migrating Power BI reports.
Relationship to DMV:
Corresponding DMV: The INFO.FORMATSTRINGDEFINITIONS function essentially wraps the functionality of querying the TMSCHEMA_FORMAT_STRING_DEFINITIONS DMV, which is part of the Analysis Services schema for tabular models. DMVs in this context are used to expose metadata about the model's structure, including how data is formatted.
Usage: Like other INFO functions introduced in Power BI, this allows for DAX queries to directly access model metadata without needing to connect to the model through other means like DAX Studio or directly to an Analysis Services server.
Limitations:
Context Transition: The function performs a context transition if called in a row context, meaning the evaluation might change based on the row context in which it's called.
Restrictions: It cannot be used in calculated tables or calculated columns due to its metadata querying nature, which is more suited for report or model exploration rather than data transformation.
Given this, INFO.FORMATSTRINGDEFINITIONS serves as a DAX interface to the underlying DMV, providing a user-friendly way to query format string metadata without needing to delve directly into SQL or DMV syntax. However, specific usage or detailed examples beyond this description would require direct access to the Power BI model or further documentation not covered in the search results provided.
Here's an example of how INFO.FORMATSTRINGDEFINITIONS might be used in Power BI Desktop's DAX Query View:
Example Query
You would typically use this function in the DAX Query View to retrieve metadata about format strings defined in your Power BI model. Here's a basic example to fetch all format string definitions:
dax
EVALUATE
INFO.FORMATSTRINGDEFINITIONS()
This query would return a table with columns that correspond to the TMSCHEMA_FORMAT_STRING_DEFINITIONS DMV, providing details like:
FORMAT_STRING_DEFINITION_ID: Unique identifier for each format string definition.
NAME: The name of the format string.
FORMAT_STRING: The actual format string expression.
DESCRIPTION: A description if provided for the format string.
CULTURE: The culture for which the format string is defined if culture-specific.
Example with Restrictions
If you want to filter the results to show only format strings associated with a specific measure or object, you might use:
dax
EVALUATE
INFO.FORMATSTRINGDEFINITIONS(
"MEASURE_ID", "MeasureIDFromYourModel",
"OBJECT_TYPE", "Measure"
)
Here:
"MEASURE_ID" and "MeasureIDFromYourModel" would be replaced with actual identifiers from your Power BI model. "MEASURE_ID" is the restriction name, and "MeasureIDFromYourModel" is the specific value you're filtering by.
"OBJECT_TYPE" and "Measure" specify that you're looking for format strings applied to measures.
Use Case in a Report
While you can't use INFO.FORMATSTRINGDEFINITIONS directly in measures or calculated columns for data transformation, here's how you might leverage this information in a report:
Documentation: Run this query to generate a report or export the data to document all the format strings used in your model. This can be useful for model maintenance or when handing over the model to another team.
Model Analysis: Use the output to analyze how different parts of your data are formatted, which can be crucial when dealing with international data where different cultures might require different number, date, or currency formats.
Debugging: If you encounter issues with data display or formatting in your visuals, this query can help identify where and how format strings are applied.
Remember, these queries are typically run in Power BI Desktop's DAX Query View or similar tools like DAX Studio, not within the measures or calculated columns of the model itself. The exact column names and structure returned by INFO.FORMATSTRINGDEFINITIONS might vary slightly based on Power BI's implementation, but the core concept remains as described.
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