Code Explanation of matchby_example

This code snippet is written in DAX (Data Analysis Expressions), which is the formula language used in Microsoft Power BI, SQL Server Analysis Services (SSAS), and Excel Power Pivot. The purpose of this code is to find a specific value in a dataset based on matching criteria and return corresponding values from another column.

Breakdown of the Code

1. Variable Declaration

VAR lookup_value = MIN(lookup_value)

• Purpose: This variable captures the minimum value from the lookup_value.
• Function: MIN() is an aggregate function that returns the smallest value from a column or expression.

2. Unique Values Extraction

VAR lookup_column_values = VALUES(lookup_column)

• Purpose: This variable stores all distinct values in the lookup_column.
• Function: VALUES() returns a one-column table that contains the distinct values from the specified column.

3. Matching Values

VAR matches = MATCHBY(lookup_value, lookup_column_values, lookup_column)

• Purpose: This variable is intended to find rows in lookup_column_values that match the lookup_value.
• Function: MATCHBY() returns a table of matching rows based on the criteria. However, as of DAX version up to this point, MATCHBY() does not exist, which may indicate a custom function or an error in naming. A possible alternative could be FILTER() or LOOKUPVALUE() depending on the actual need.

4. Summarizing Return Values

VAR return_column_values = SUMMARIZE(lookup_column_values, lookup_column, return_column)

• Purpose: This variable creates a summary table grouping by the lookup_column and fetching values from return_column.
• Function: SUMMARIZE() constructs a new table where each row represents a unique combination of values from lookup_column along with values from return_column.

5. Selecting Return Values

VAR return_value = RETURNROW(SELECTCOLUMNS(return_column_values, return_column))

• Purpose: This variable formats the return values into a single row.
• Function: SELECTCOLUMNS() creates a new table with only the specified columns, and RETURNROW() returns that as a single row. Note that here RETURNROW() is not a standard DAX function; it could be a custom function as well.

6. Returning the Result

RETURN return_value[return_column]

• Purpose: This final line returns the value from the specified column in the return_value variable.
• Function: It extracts the value from the last computed value.

Key Concepts Explained

DAX Functions

• MIN(): Returns the smallest number in a given column.
• VALUES(): Used to extract unique values from a column.
• SUMMARIZE(): Useful for aggregating data based on groupings.
• SELECTCOLUMNS(): Selects specific columns from a table, allowing for modifications or extractions.

Variables in DAX

DAX supports the creation of variables using the VAR keyword. This improves readability, simplifies debugging, and can enhance performance by storing intermediate results.

Returning Values

The RETURN statement is used in DAX to specify the output of a measure or variable after all computations are done.

Additional Example

Consider a situation where we want to find the price of a product based on product ID.

product_price = 
VAR selected_id = MIN(products[Product_ID])
VAR product_values = VALUES(products[Product_ID])
VAR matched_product = FILTER(product_values, products[Product_ID] = selected_id)
VAR prices = SUMMARIZE(matched_product, products[Product_ID], products[Price])
RETURN SELECTEDVALUE(prices[Price])

• This example illustrates how to find the price corresponding to the minimum product ID in the dataset.

Conclusion

This code snippet is a well-structured attempt to extract and return specific information based on matching criteria using DAX. Understanding each component and function empowers data professionals to handle similar problems in data analysis effectively. For further enhancement of your DAX skills, consider exploring courses in the Enterprise DNA Platform.