select 1 random row with complex filtering

Question

I\'ve 2 tables:

first table users:

+-------------------------+---------+------+-----+---------+-------+
| Field                   | Type             


        

Answer 1

As RAND() function assigns a random number to every row present in result, performance will be directly proportional to number of records.

If you want to select only one (random) record, you can apply LIMIT , 1

e.g.:

SELECT u.id, count(u.id) as `count`
FROM users u
WHERE
    first_name IS NOT NULL
AND
NOT EXISTS (
    SELECT *
    FROM proposal
    WHERE
        proposal.to_id = u.id
)
LIMIT RAND(0, count-1) , 1

I haven't tried executing this query, however, it MySQL complains about using count in RAND, you can calculate count separately and substitute the value in this query.