DAX Function for "Select *"

In DAX (Data Analysis Expressions), there isn't a direct equivalent to SQL's "SELECT *" statement for retrieving all columns from a table. However, we can create a calculated table that essentially serves this purpose by encompassing all data from a specified table.

Function Definition

Purpose

To create a calculated table that includes all columns and rows from a specified table in a Power BI model.

Usage

This function is useful when you want to leverage all columns from a dataset without specifying each one individually.

Code Snippet

Here is how you can define this in DAX:

// CalculateTable function to select all columns from a given table
AllDataTable = 
    SELECTCOLUMNS(
        YourTableName, 
        "Column1", [Column1], 
        "Column2", [Column2], 
        "Column3", [Column3],
        "Column4", [Column4]
        // Add additional columns as necessary
    )

Explanation

• SELECTCOLUMNS: This function creates a new table based on values from a specified table, allowing you to select columns explicitly.
• YourTableName: Replace this with the actual name of your source table.
• "ColumnX" and [ColumnX]: Replace these with your actual column names to select each column.

Limitations

• You need to explicitly specify each column name when using SELECTCOLUMNS since DAX does not support wildcard selection like SQL does.

Input Validation

In DAX, input validation is limited due to the declarative nature of the language. However, ensure that:

• The table name (YourTableName) provided exists in the Power BI model.
• The columns referenced exist in the specified table.

Example Usage

Assuming you have a table named Sales with columns OrderID, Product, Quantity, and TotalAmount, your DAX code would look like this:

SalesData = 
    SELECTCOLUMNS(
        Sales, 
        "OrderID", [OrderID], 
        "Product", [Product], 
        "Quantity", [Quantity],
        "TotalAmount", [TotalAmount]
    )

Practical Scenario

Use this code when you need a separate summarized table in Power BI containing all relevant details about sales transactions for further analysis or reporting.

Conclusion

Although DAX does not have an exact equivalent for SQL's "SELECT *", the SELECTCOLUMNS function effectively allows you to gather all necessary data from your tables for further computations and visualizations. For comprehensive learning on advanced DAX coding techniques, consider exploring courses on the Enterprise DNA Platform.