LIMIT then RAND rather than RAND then LIMIT

问题

I'm using full text search to pull rows.
I order the rows based on score (ORDER BY SCORE) , then of the top 20 rows (LIMIT 20), I want to rand (RAND) the result set.

So for any specific search term, I want to randomly show 5 of the top 20 results.

My workaround is code based- where I put the top 20 into an array then randomly select 5.

Is there sql way to do this?

回答1:

You can do this using an inner select. Select the top twenty rows in the inner select. In the outer select order these rows randomly and select the top five:

SELECT *
FROM (
    SELECT *
    FROM table1
    ORDER BY score DESC
    LIMIT 20
) AS T1
ORDER BY RAND()
LIMIT 5

来源：https://stackoverflow.com/questions/2648076/limit-then-rand-rather-than-rand-then-limit