How to perform bulk data updates in SQL?

[LowkeyM]

I have multiple tables like the one in the image at http://prntscr.com/g26xkz. I want to input 'f' under 8 and 'g' under 7. I don't want to change the entire table; I just want to change two columns and have the same data in all subsequent columns (meaning, 'a' in all of column 3, 'b' in column 4, etc.). Is there an easy code solution where I can save a code to be used in one row and then have it change all rows?