POW – Explain That SQL #1

Someone asked me to quickly write them some code in any language that would accomplish a certain task. The following, which is in PostgreSQL, is the second solution that I came up with after doing the first one in my favorite language, JavaScript:

    SELECT CHR(num
        + CASE
            WHEN num < 26 THEN 65
            WHEN num BETWEEN 26 AND 51 THEN 71
            ELSE -4
    FROM (
      SELECT FLOOR(RANDOM() * 62)::INT AS num,
        generate_series(1, 12)
    ) AS t
  ), '')

The question is, what does this SELECT statement actually do? If you were asked to write that as a JavaScript, substituting the 12 for a variable passed into the function, what would your function look like?

As usual, the answer to this Problem of the Week will be made available a week from today, on Wednesday, August 22, 2012.

The answer to this Problem of the Week can now be found here.

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