ORDER BY RAND() seems to be less than random

Question

I have a fairly simple SQL (MySQL):

SELECT foo FROM bar ORDER BY rank, RAND()

I notice that when I refresh the results, the randomness is s

Answer 1

The RAND() can not be refresh for each row. A possible solution might be:

SELECT foo FROM bar ORDER BY rank, CHECKSUM(NEWID())

Answer 2

RAND() is only executed once per query. You can verify this by looking at the result set.

If you're trying to get a randomized order, you should be using either NEWID() or CHECKSUM(NEWID()).

WITH T AS ( -- example using RAND()
  SELECT 'Me' Name UNION SELECT 'You' UNION SELECT 'Another'
)
SELECT Name, RAND()
FROM T;

WITH T AS ( -- example using just NEWID()
  SELECT 'Me' Name UNION SELECT 'You' UNION SELECT 'Another'
)
SELECT Name, NEWID()
FROM T;

WITH T AS ( -- example getting the CHECKSUM() of NEWID()
  SELECT 'Me' Name UNION SELECT 'You' UNION SELECT 'Another'
)
SELECT Name, CHECKSUM(NEWID())
FROM T;