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Power Query: All Change for Values

5 August 2020

Welcome to our Power Query blog. This week, I look at replacing values in all columns in a table.

I have the following data, and I decide to select all my columns and replace the null values with a space:

I click ‘OK’ and Power Query generates a line of M code for my step.

The M code generated is:

= Table.ReplaceValue(#"Duplicated Column",null," ",Replacer.ReplaceValue,{"Column1", "Column2", "Column3", "Index", "Column3 - Copy"})

This code clearly relies on the column names staying the same.  I want to adjust this step so that the column names are calculated right before I replace the null values. I can do this by using Table.ColumnNames():

Table.ColumnNames(table as table) as list

This function returns the column names in the table as a list of text.

Since each step is a table, I can use the step name:

I can now see a list of my column names.  The M code I have used is:

= Table.ColumnNames(#"Duplicated Column")

This refers to the step before ‘Replaced Value’.  I can then change my ‘Replaced Value’ step to use this list. 

The M code I have used is:

= Table.ReplaceValue(#"Duplicated Column",null," ",Replacer.ReplaceValue,Custom1)

This means I am using the list generated in the ‘Custom1’ step to replace values in the ‘Duplicated Column’ step.  I have generated the steps in this order to show the process.  It’s best to create the list before trying to replace the values in practice!


Come back next time for more ways to use Power Query!