MySQL Query避免使用变量

Question

有没有办法将第一个查询放入主查询并避免设置变量？

SET @domain_id = (SELECT id FROM stop_domain LIMIT 1);
SELECT
  IFNULL(MAX(duid), 0) + 1 AS duid
  , @domain_id
FROM
  stop_link
WHERE domain_id = @domain_id;

stop_domain

id | url

stop_link

id | duid | domain_id

Answer 1

SELECT     IFNULL(MAX(duid), 0) + 1 AS duid
           ,t.id
FROM       (SELECT id FROM stop_domain LIMIT 1) t
INNER JOIN stop_link
ON         domain_id = t.id
GROUP BY   t.id;

Answer 2

确实有，

SELECT
  IFNULL(MAX(duid), 0) + 1 AS duid
  , domain_id
FROM
  stop_link
WHERE domain_id = (SELECT id FROM stop_domain LIMIT 1);