Postgresql nested SELECT

I'm learning postgresql and I can't figure out how to write this nested query or if it's even possible.

Table -> Points: pid | val

Table -> Grid: gid | max开发者_如何学Go_val | min_val

Return I want: pid | gid | val

This is how I see it in my head

for p in (SELECT * FROM Points)
    SELECT gid FROM Grid AS g WHERE p.val < g.max_val AND p.val > g.min_val   

Is this possible? If so can someone point me in the right direction?

I wouldn't think you need a nested query, just a join. Does something like this give what you need?

SELECT
  P.pid,
  G.gid,
  P.val
FROM
  Grid          AS G
INNER JOIN
  Points        AS P
    ON  P.val < g.max_val
    AND P.Val > g.min_val

Following query will always return point even if point's val is not in any grid range - in such case gid will be NULL:

SELECT
  p.pid,
  g.gid,
  p.val
FROM
  Points p
  LEFT JOIN Grid g ON g.min_val > p.val AND g.max_val < p.val

If there is more than one Grid with a range that will match the point's val, query will return two rows for each gid.

If you want to return only points matching any grid, just add a condition:

WHERE
  g.gid IS NOT NULL