查询中也有'null'的结果

Question

以下是存储我的数据的3个表：

答案

answer_id | question_id | answer

问题

question_id | question

users_answers

user_answer_id | answer_id | question_id

我在实践中要做的事情：

对于给定的问题，请收集所有答案，并计算有多少人回答了A或B。 这里的重点是，即使没有人选择它作为可能的好答案，我也需要所有答案。

这是我进行的查询：

SELECT   q.question_id,
         q.question,
         a.answer_id,
         a.answer
FROM     questions AS q
    JOIN answers AS a ON
         q.question_id = a.question_id
    JOIN users_answers ON
         a.answer_id = users_answers.answer_id
WHERE q.question_id = 19

这是我的实际结果（带有示例）：

question_id    |    question    |    answer_id    |    answer

     19             'blabla'             12           'C blabla'
     19             'blabla'             12           'C blabla'
     19             'blabla'             10           'A blabla'
     19             'blabla'             13           'D blabla'

没有用户给出“ B blabla”作为可能的好答案，但是我的结果中仍然需要此结果。

我该怎么做？

非常感谢您

Answer 1

SELECT questions.question_id, 
       questions.question, 
       answers.answer_id, 
       answers.answer, 
       (SELECT Count(users_answers.user_answer_id) 
        FROM   users_answers 
        WHERE  users_answers.question_id = 1 
               AND users_answers.answer_id IN ( 1, 2 )) AS 
       total_people_answered_anserA_B 
FROM   users_answers 
       INNER JOIN questions 
               ON questions.question_id = users_answers.question_id 
       INNER JOIN answers 
               ON answers.answer_id = users_answers.answer_id 
WHERE  users_answers.question_id = 1;