Replace blank spaces with null values

I am rolling up a huge table by counts into a new table, where I want to make all the empty strings as null, and typecast some columns as well. I read through some of the posts and I could not find a query, which would let me do it across all the columns in a single query, without using multiple statements.

Let me know if it is possible for me to iterate across all columns and replace cells with empty strings with null.

Ref: convert empty space to null

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