如何在mysql中获得所有未回答的问题

我有两张桌子，回答和提问。所有问题都插入问题BL中，答案也插入问题BL中。现在，我想通过参考答案BL来获得尚未被任何人回答的问题。这是我的疑问：

 "SELECT * FROM questionstbl LEFT JOIN answerstbl ON answerstbl.qu_id=questionstbl.qu_id 
  GROUP BY ans_id"

然而，结果是有答案的问题

有人知道吗？

类似这样的事情：

SELECT * FROM questionstbl WHERE qu_id NOT IN (SELECT qu_id FROM answerstbl)

大概是这样的：

SELECT * FROM questionstbl WHERE qu_id NOT IN (SELECT qu_id FROM answerstbl)

---

您可以在比较运算符中使用

NOT

查询

Select * from questionstbl  
where qu_id not in(
    select distinct qu_id from answerstbl
);

select
questionstbl.qu_id as questionId,
answerstbl.ans_id as answersId,
from questionstbl, answerstbl
LEFT JOIN answerstbl ON answerstbl.qu_id=questionstbl.qu_id 
where (condition to check questions that are NOT YET answered)
GROUP BY ans_id;

您可以在比较运算符中使用
NOT

查询

Select * from questionstbl  
where qu_id not in(
    select distinct qu_id from answerstbl
);

select
questionstbl.qu_id as questionId,
answerstbl.ans_id as answersId,
from questionstbl, answerstbl
LEFT JOIN answerstbl ON answerstbl.qu_id=questionstbl.qu_id 
where (condition to check questions that are NOT YET answered)
GROUP BY ans_id;

因此，您希望所有问题的答案表中不存在该问题id

SELECT Q.*
FROM questionstbl Q
WHERE NOT EXISTS(SELECT 1 FROM answerstbl A WHERE A.qu_id = Q.qu_id )

或者像这样

SELECT Q.*
FROM questionstbl Q
WHERE 
  Q.qu_id NOT IN (SELECT qu_id FROM answertbl)

因此，您希望所有问题的答案表中不存在该问题id

SELECT Q.*
FROM questionstbl Q
WHERE NOT EXISTS(SELECT 1 FROM answerstbl A WHERE A.qu_id = Q.qu_id )

或者像这样

SELECT Q.*
FROM questionstbl Q
WHERE 
  Q.qu_id NOT IN (SELECT qu_id FROM answertbl)

另一个选择是：

Select questions.qu_id, questions.question from questions INNER JOIN answers where questions.qu_id <> answers.qu_id

选择questions.qu\u id，questions.question from questions internal JOIN answers where questions.qu\u id answers.qu\u id

上面的查询结果是尚未回答的问题表中的所有问题。但是，您的查询中有一个错误，您希望得到没有答案的问题，并且您正在根据答案id对它们进行分组（这些问题的答案id不存在）。
另一个选项可以是：

Select questions.qu_id, questions.question from questions INNER JOIN answers where questions.qu_id <> answers.qu_id

选择questions.qu\u id，questions.question from questions internal JOIN answers where questions.qu\u id answers.qu\u id

上面的查询结果是尚未回答的问题表中的所有问题。但是，您的查询中有一个错误，您希望得到没有答案的问题，并且您正在根据答案id对这些问题进行分组（这些问题不存在答案id）。
应根据表中的字段输入要检查的条件，如果可以指定表字段，则可以填写条件

查询

Select * from questionstbl  
where qu_id not in(
    select distinct qu_id from answerstbl
);

select
questionstbl.qu_id as questionId,
answerstbl.ans_id as answersId,
from questionstbl, answerstbl
LEFT JOIN answerstbl ON answerstbl.qu_id=questionstbl.qu_id 
where (condition to check questions that are NOT YET answered)
GROUP BY ans_id;

应根据表中的字段输入要检查的条件，如果可以指定表字段，则可以填写条件

查询

Select * from questionstbl  
where qu_id not in(
    select distinct qu_id from answerstbl
);

select
questionstbl.qu_id as questionId,
answerstbl.ans_id as answersId,
from questionstbl, answerstbl
LEFT JOIN answerstbl ON answerstbl.qu_id=questionstbl.qu_id 
where (condition to check questions that are NOT YET answered)
GROUP BY ans_id;

看一看，看一看