Overview of DAX and DAX Query View in Power BI

We will discuss DAX before moving on to knowing DAX Query View.

DAX is nothing but Data Analysis Expression which is formula expression language used in Analysis Services, Power BI and Power Pivot in Excel. DAX formula includes functions, operator and values to perform operations on Table and Data. DAX formulas are used in measures, calculated columns, calculated tables, and row-level security.

Measure: Measures are dynamic calculation formulas where the results change depending on context

Total Profit = SUM(Orders[Profit])        

Calculated Columns: A calculated column is a column that you add to an existing table (in the model) and then create a DAX formula that defines the column's values.

Full Name = CONCATENATE(Customers[First Name], Customer[Last Name])        

Calculated tables: A calculated table is a computed object, based on a formula expression, derived from all or part of other tables in the same model

Dates Table = CALENDAR(DATE(2023, 1,1), DATE(2023,12,31))        

Context:

When developing DAX formulas, the results of a formula adjust to reflect the current row or cell selection as well as any connected data, context is what makes dynamic analysis possible. Comprehending and utilizing context proficiently is essential for constructing dynamic, high-performing studies and fixing formulaic issues.

There are different types of context: row context, query context, and filter context

Row Context: "The current row" might be considered the row context. When we build a formula in a calculated column, the values from every column in the current row are included in the formula's row context. All the data from the other table that are relevant to the current row are also included in the content if the table is associated to another table.

Query Context: The subset of data that is implicitly obtained for a formula is referred to as query context. The engine looks at row and column headers, slicers, and report filters, for instance, when a user inserts a measure or field into a report in order to ascertain the context. After that, the required queries are applied to the model data in order to obtain the appropriate subset of data, perform the computations specified by the formula, and finally add values to the report.

Filter Context: The set of values permitted in each column or in the values obtained from a linked table is known as the filter context. Filters can be used in the presentation layer (PivotTables and reports) or on the column in the designer. Filter expressions within the formula can also be used to define filters explicitly.

When you use formula arguments to put filter constraints on the range of values that are permitted in a column or table, filter context is added. Row context and query context are two examples of contexts that are superseded by filter context.

?DAX Query View

One tool in Power BI Desktop that lets you see and manipulate Data Analysis Expressions (DAX) queries inside your semantic models is called DAX Query View.

The following provides a thorough breakdown of its elements and features:

DAX Queries

EVALUATE Statement: This section of the query that defines what data is returned and how to return it is mandatory.

DEFINE Statement: You can define measurements and other DAX formulas that can be used in the query with this optional statement.

DAX Query View Opens

Selecting the relevant icon on the left side of Power BI Desktop will allow you to enter the DAX Query View.

DAX Query View Layout

Ribbon: Provides standard actions for DAX query writing.

Format Query: Helps to better arrange the current query for readability.

Comment/Uncomment: This feature lets you delete or comment out lines.

Find and Replace: This feature lets you look for text inside the DAX query editor and replace it.

Command Palette: A convenient way to access different commands.

Analyzer of Performance

To see out how visuals impact performance, you can obtain visual DAX queries from the Performance Analyzer.

It's crucial to remember that DAX queries do not produce objects in the model or visualizations in the report; rather, they are used to retrieve data from the model. In that regard, they are comparable to SQL queries.

For a more practical method, you can easily query your data model by using the pre-existing DAX query syntax by creating and executing DAX queries using the DAX Query View. BI developers who previously relied on third-party tools or APIs to create and execute DAX queries may find this functionality especially helpful.

Remember, the DAX Query View is currently in preview, so some features might be subject to change as the product evolves. For the most up-to-date information and tutorials, you can refer to the official Power BI documentation.

Reference:

https://learn.microsoft.com/en-us/power-bi/transform-model/dax-query-view

https://learn.microsoft.com/en-us/dax/

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