编写SQL子查询时出现问题

我知道我一定缺少了一些简单的东西……但我在编写SQL子查询时遇到了问题。鉴于以下数据

user_id question_id answer_text
89          1           value1
89          2           value2
80          2           value2
99          2           value2
96          1           value1
96          2           value2
111        1           value1
111        2           value2

我需要获取同时具有question_id 1='value1'和question_id 2='value2'的用户

以上结果是使用此查询生成的：

SELECT `User_answer`.`user_id`, `User_answer`.`question_id`, `User_answer`.`answer_text` FROM `user_answers` AS `User_answer` WHERE `User_answer`.`question_id` IN (1, 2) AND `User_answer`.`answer_text` IN ('value1', 'value2')

但当然，这会返回回答问题1的用户的值为1，而回答问题2的用户的值与回答问题2的值完全不同，反之亦然

---

我需要能够添加更多的条件，但我想我可以添加，如果我至少可以让这两个工作。

一种方法是使用自连接，例如

select a1.user_id, a1.answer_text AS Answer1, a2.answer_text AS Answer2
from user_answers a1 join user_answers a2 on a1.userid=a2.userid and a1.question_id=1     and a2.question_id=2
where a1.answer_text <> a2.answer_text

---

抱歉，如果语法有点不正确，我已经有一段时间没有使用MySQL了，但是你明白了

我会使用这样的内部联接来完成此操作：

SELECT
  user_id
FROM
  user_answers AS a1
  INNER JOIN user_answers AS a2 ON
    a2.user_id = a1.user_id
    AND a2.question_id=2
    AND a2.answer_text='value2'
WHERE
  a1.question_id=1
  AND a1.answer_text='value1'

SELECT `User_answer`.`user_id`, 
  MAX(CASE `User_answer`.`question_id` WHEN 1 THEN `User_answer`.`answer_text` END) AS `q1_answer`,
  MAX(CASE `User_answer`.`question_id` WHEN 2 THEN `User_answer`.`answer_text` END) AS `q2_answer`
FROM `user_answers` AS `User_answer` 
WHERE (`User_answer`.`question_id` = 1 AND `User_answer`.`answer_text` = 'value1')
  OR  (`User_answer`.`question_id` = 2 AND `User_answer`.`answer_text` = 'value2')
GROUP BY `User_answer`.`user_id`
HAVING COUNT(DISTINCT `User_answer`.`question_id`) = 2;

翻译为：

查找问题id为1且答案文本为“value1”的所有答案 对于这些答案，请查找具有相同用户id和问题id为2以及答案文本为“value2”的相应答案。 把两者都不满意的东西扔掉。

---

我会尝试在不使用子查询的情况下执行此操作，如下所示：

SELECT
  user_id
FROM
  user_answers AS a1
  INNER JOIN user_answers AS a2 ON
    a2.user_id = a1.user_id
    AND a2.question_id=2
    AND a2.answer_text='value2'
WHERE
  a1.question_id=1
  AND a1.answer_text='value1'

SELECT `User_answer`.`user_id`, 
  MAX(CASE `User_answer`.`question_id` WHEN 1 THEN `User_answer`.`answer_text` END) AS `q1_answer`,
  MAX(CASE `User_answer`.`question_id` WHEN 2 THEN `User_answer`.`answer_text` END) AS `q2_answer`
FROM `user_answers` AS `User_answer` 
WHERE (`User_answer`.`question_id` = 1 AND `User_answer`.`answer_text` = 'value1')
  OR  (`User_answer`.`question_id` = 2 AND `User_answer`.`answer_text` = 'value2')
GROUP BY `User_answer`.`user_id`
HAVING COUNT(DISTINCT `User_answer`.`question_id`) = 2;