Update PSQL rows with different random values each

Question

I'm trying to batch update each row from a table, assigning them an individual location. This is the query I am using

UPDATE point SET location=
  ST_PointFromText('POINT(' || 
  (SELECT random()+5) || ' ' ||
  (SELECT random()+5) || ')', 4326) 
  WHERE parent_id=100;

The problem is that each row will then receive the exact same value.

Answer 1

I found this article by Szymon Lipiński that touches on my problem. Here is how I fixed the query:

UPDATE point p SET location=
  ST_PointFromText('POINT(' || 
  ((SELECT random() WHERE p=p)+5) || ' ' ||
  ((SELECT random() where p=p)+5) || ')', 4326) 
  WHERE parent_id=100;

An outer dependency is needed in order to force PostgreSQL to reevaluate the expression each time.