Mysql 使用UNION时有2个不同的字段

我想在一个结果表中显示两个查询，其中包含两个字段。错误答案和正确答案

错误答案查询：

select count(ma_id) as wrong_answers
from exercicio natural
join avaliacao natural
join user_sessao
where se_id=4 and us_id=1 and not exists (
    select ma_id
    from grelha natural
    join exercicio natural
    join avaliacao natural
    join user_sessao
    where us_id=1 and se_id=4
)

select count(ma_id) as right_answers
from exercicio natural
join avaliacao natural
join user_sessao natural
join grelha where se_id=4 and us_id=1

右键回答查询：

select count(ma_id) as wrong_answers
from exercicio natural
join avaliacao natural
join user_sessao
where se_id=4 and us_id=1 and not exists (
    select ma_id
    from grelha natural
    join exercicio natural
    join avaliacao natural
    join user_sessao
    where us_id=1 and se_id=4
)

select count(ma_id) as right_answers
from exercicio natural
join avaliacao natural
join user_sessao natural
join grelha where se_id=4 and us_id=1

当我执行

错误答案

查询

联合正确答案

查询时，两个结果都显示在错误答案列中

如何使它们成为2个不同的列

---

谢谢

UNION ALL

保留两个结果集中的列。如果一列同时出现在两个查询中，那么它将在最终结果集中出现一次。

在这种情况下，您不需要联合查询，如果您希望这些查询位于两个不同的列中，可以使用以下方法：

SELECT NULL AS correct, count(ma_id) AS wrong
.... wrong answer stuff here

UNION ALL

SELECT count(ma_id), NULL
.... right answer stuff here

SELECT
  (
    select count(ma_id) as wrong_answers
    from exercicio
    natural join avaliacao
    natural join user_sessao
    where se_id=4 and us_id=1 and not exists (
       select ma_id
       from grelha
       natural join exercicio
       natural join avaliacao
       natural join user_sessao
       where us_id=1 and se_id=4
    )
  ) AS wrong_answers,
  (
    select count(ma_id) as right_answers
    from exercicio
    natural join avaliacao
    natural join user_sessao
    natural join grelha
    where se_id=4 and us_id=1
  ) AS right_answers;

---

尝试使用

UNION ALL