在MySql中结合两个select语句？

Question

我有这张桌子，看看那里。

create table if not exists thread_question
   (
    question_id INT NOT NULL auto_increment,
    first_name VARCHAR(100) NOT NULL,
    last_name VARCHAR(100) NOT NULL,
    question_title VARCHAR(500) NOT NULL,
    question VARCHAR(100000) NOT NULL,
    question_dateTime VARCHAR(100) NOT NULL,
    PRIMARY KEY(question_id)
  );

create table if not exists thread_answer
 (
  answer_id INT NOT NULL auto_increment,
  question_id INT NOT NULL references thread_question(question_id),
  first_name VARCHAR(100) NOT NULL,
  last_name VARCHAR(100) NOT NULL,
  answer VARCHAR(100000) NOT NULL,
  answer_dateTime VARCHAR(100) NOT NULL,
  PRIMARY KEY(answer_id)
 );

实际上，我正在创建一个论坛来显示答案，它运行良好。您还可以看到question_id 的列已插入thread_question 以及thread_answer。我想在一页中显示我的答案，有多少用户在那里发布了答案。

所以我可以根据这个问题做到这一点 -> How to show the numbers of answers posted into my forum?

问题

现在我正在尝试将这两个语句结合起来：

第一句话：

SELECT thread_question.question_id, COALESCE(sub.counts,0) AS NumerOfAnswer 
   FROM thread_question LEFT JOIN (
        SELECT question_id, COUNT(answer_id) AS counts
        FROM thread_answer
        GROUP BY question_id
    ) sub ON thread_question.question_id = sub.question_id ORDER BY NumerOfAnswer asc

第二个陈述：

select * from thread_question

其实我想从thread_question's table获取user's first and second name、question和question's title。

我确实使用UNION and UNION ALL 和SELECT( SELECT..)(SELECT..)。
但我无法显示结果。每次都给我一个错误。

请帮忙！！
当然，我们将不胜感激！

Answer 1

由于您已经在查询中有thread_question 表，因此您只需添加thread_question.* 即可添加剩余的列，如下所示：

SELECT
    thread_question.* -- <<== Use .* to bring all fields
,   COALESCE(sub.counts,0) AS NumerOfAnswer 
FROM thread_question
LEFT JOIN (
    SELECT question_id, COUNT(answer_id) AS counts
    FROM thread_answer
    GROUP BY question_id
) sub ON thread_question.question_id = sub.question_id
ORDER BY NumerOfAnswer asc