Get data from column from unrelated tables

Hi,

I tried to add comments into the code like below.

TABLE C =
    ADDCOLUMNS (
        'Table A',
        // Use the ADDCOLUMNS function to create a new calculated column within 'Table A'
        "@letter",
            // Name the calculated column as "@letter"
            // Define the expression for the "@letter" column
            MINX (
                // Use the MINX function to return the minimum value of the expression specified
                // This ensures we get the smallest (alphabetically or numerically) 'letter' value
                FILTER (
                    // Use the FILTER function to create a subset of 'Table B'
                    // The subset includes rows where both conditions below are true:
                    'Table B',
                    'Table B'[id] = 'Table A'[id] // Condition 1: Match the 'id' in 'Table B' with the 'id' in 'Table A'
                        && 'Table B'[code] = 'Table A'[code] // Condition 2: Match the 'code' in 'Table B' with the 'code' in 'Table A'
                ),
                // The column from 'Table B' to evaluate: 'Table B'[letter]
                // This is the column from which we want to extract the minimum value
                'Table B'[letter]
            )
    )

I was more hoping to use DAX as I was aware on how to do this in PQ. Also I was hoping for the table to look like this as I want to take only some columns from table A. what if table had 4 or more columns (example below) and we wanted to use only first three columns in this calculation to get same output. Is there a way for this whole code to get wrapped up with selectcolumns?