Question

Let’s say I have a subtable called result.

SELECT school, grade 
  FROM (SELECT school, grade 
          FROM simulated_records 
         LIMIT 10) as result

How would i update the columns of this subtable? I tried:

UPDATE result 
   SET grade = 'A' 

…but I get an error.

Answer 1

sub*selects* are temporary, they can’t be updated. It sounds like you want a temporary table

CREATE TEMP TABLE temp_grades AS
SELECT school, grade FROM simulated_records;
UPDATE temp_grades SET grade = 'A';

EDIT: re your comment:

UPDATE simulated_records
FROM (SELECT id FROM simulated_records WHERE school='Yale' LIMIT 10) AS result
SET grade='A'
WHERE id = result.id
RETURNING *;

The above uses the UPDATE FROM table operation using a subselect

EDIT 2: for second comment:

Assuming you don’t have a typo maybe you have an old version. There’s an alternative way to do this with better support:

UPDATE simulated_records SET grade = 'A' WHERE id IN
  (SELECT id FROM simulated_records WHERE school = 'Yale' LIMIT 10);