Quartiles in SQL query

Question

I have a very simple table like that:

CREATE TABLE IF NOT EXISTS LuxLog (
  Sensor TINYINT,
  Lux INT,
  PRIMARY KEY(Sensor)
)

It contains

Answer 1

Well to use NTILE is very simple but it is a Postgres Function. You basically just do something like this:

SELECT value_you_are_NTILING,
    NTILE(4) OVER (ORDER BY value_you_are_NTILING DESC) AS tiles
FROM
(SELECT math_that_gives_you_the_value_you_are_NTILING_here AS value_you_are_NTILING FROM tablename);

Here is a simple example I made for you on SQLFiddle: http://sqlfiddle.com/#!15/7f05a/1

In MySQL you would use RANK... Here is the SQLFiddle for that: http://www.sqlfiddle.com/#!2/d5587/1 (this comes from the Question linked below)

This use of MySQL RANK() comes from the Stackoverflow answered here: Rank function in MySQL

Look for the answer by Salman A.