mysql查询顺序和连接串联字符串

Question

我有这个问题：

SELECT 
  CONCAT(users.id, '#_#', users.nickname, '#_#', users.avatar, '#_#',
         questions.datetime,'#_#',questions.question,'#_#',0000) as summary
FROM
  `questions` join users
  on users.id = questions.id_user 
WHERE
  questions.id = 12 
UNION 
SELECT
  CONCAT(users.id, '#_#', users.nickname, '#_#', users.avatar, '#_#',
         answers.datetime,'#_#',answers.answer,'#_#',answers.id) as summary 
FROM
  answers join users
  on users.id = answers.id_user where id_question = 12

此查询必须以一列（带有连锁数据）结果，我需要通过answers.datetime排序，但我自己无法找到解决方案......

有些mysql大师可以帮帮我吗？

谢谢：）

Answer 1

SELECT * FROM (
  SELECT datetime,
    CONCAT(users.id,'#_#',users.nickname,'#_#',users.avatar,'#_#',questions.datetime,'#_#',questions.question,'#_#',0000) as summary 
  FROM `questions` 
  join users on users.id = questions.id_user 
  WHERE questions.id = 12 
  union 
  select datetime,
    CONCAT(users.id,'#_#',users.nickname,'#_#',users.avatar,'#_#',answers.datetime,'#_#',answers.answer,'#_#',answers.id) as summary 
  from answers 
  join users on users.id = answers.id_user where id_question = 12
) A ORDER BY datetime

假设您打算按datetime排序，而不是answers.datetime。