How to ignore ANY STEP if THAT STEP is irrelevant

[Keith011]

Hi there

How can I dynamically ignore ANY STEP if the step is irrelevant for the current dataset

For example,

Table1

Email	Name	ID	Maths Score 1	Maths Score 2
abc@gmail.com	abc	1234	38	40

I need to change the ID as text (Using simple Change Type) and add up Maths Score 1 & Maths Score 2 (Using a Custom Column with simple addition formula). I manage to do it in Power Query

However, sometimes the dataset comes like below where there's no ID and no Maths Score 1 but in my applied step I already have Change Type and the Custom Column in place hence it will prompt an error. How can I tell Power Query that if there are any missing columns just ignore them and proceed to any subsequent step? I came across MissingField.Ignore but it doesn't work, right?

Email	Name	Maths Score 2
abc@gmail.com	abc	40

Thanks in advance!

[AlexisOlson]

I'd recommend using error handling like try ... otherwise in your steps.

For more detail, check out these resources:
https://docs.microsoft.com/en-us/power-query/error-handling

https://bengribaudo.com/blog/2020/01/15/4883/power-query-m-primer-part-15-error-handling

For nulls, in particular, you may also want to be aware of the coalesce operator:
https://gorilla.bi/power-query/coalesce/

[jennratten]

Hello - are the rows from the two tables combined at any point or are you trying to create a set of transformations to be applied separately to each table? 

[Keith011]

Hi @jennratten 

It's all within the same table, It's just that the entire table will get updated with new data & columns however some columns might not be there like ID and Maths Score 1 but the applied steps had steps that "touches" on those "missing" columns so when i hit refresh, the applied steps will hit an error saying unable to change type because "ID" wasn't found and unable to execute bla bla because Maths Score 1 wasn't found