SQL - How to reference outerquery new column in subquery

I’d like to create a new variable in an outerquery, and then manipulate this new variable in a subquery.

However, when referencing the new column in the subquery, I receive an error that no such column exists

Code:

dbGetQuery(db, 
  "SELECT id, var1/var2 AS new_var, (SELECT SUM(new_var) AS summed_var
    FROM table 
    GROUP BY id) 
  FROM table")

In this above code, the issue is that new_var doesn’t get passed to the subquery. How can I pass the newly defined column, new_var to the subquery?

EDIT: switching the inner query/outer query still doesn’t work:

dbGetQuery(db, 
  "SELECT SUM(new_var) AS summed_var (SELECT id, var1/var2 AS new_var
    FROM table)
  FROM table
  GROUP BY id")

EDIT 2: The data is structured as below. Each row is an observation for an id. I would like to generate a ratio, new_var = var1/var2 for each line. Then, I would like to sum the ratio new_var for each id. In the toy data, for example, the summed ratio for Sally would be 3/4 + 7/8.

My challenge was using GROUP BY with SQL. I was unsure how to perform GROUP BY id after generating the new_var on a line-by-line basis.

id       var1     var2    new_var
sally     3        4         3/4
susan     5        6         5/6
sally     7        8         7/8
tom       9        10        9/10