sql - 从2个表中选择

Question

我有一个表users和表questions。我想从users表中选择5个随机用户，这些用户在questions表中至少有20个查询（db.questions to_user = db.users id）。我所有人都尝试过：

SELECT * 
FROM users s 
WHERE exists (SELECT 20 
              FROM questions m 
              WHERE m.to_user = s.id) 
ORDER BY RAND() 
LIMIT 5

Answer 1

我认为这更符合您的要求：

SELECT u.*
FROM users u
WHERE (SELECT COUNT(*) FROM questions q WHERE q.to_user = u.id) >= 20
ORDER BY RAND()
LIMIT 5;