SQL加入我想要的列的两倍

Question

您好，我正在尝试通过加入 2 个视图创建一个新视图。我有 1 个视图，其中包含问题 ID 和正确答案的数量。然后另一个与错误答案的数量。我想合并它，所以它只是 question_id、correct_answer、wrong_answer。我正在使用 MySQL workbench 进行查询。

此为查看正确答案的查询

CREATE VIEW v_question_history_correct
    AS
SELECT question_id, COUNT(correctness) AS true_answer FROM skripsi_database_soal.questions_history
        WHERE correctness = 'true'
        GROUP BY question_id;

此为错误答案查看查询

CREATE VIEW v_question_history_false
AS    
SELECT question_id, COUNT(correctness) AS false_answer FROM skripsi_database_soal.questions_history
    WHERE correctness = 'false'
    GROUP BY question_id;

这是我用来连接它们的查询

SELECT * FROM v_question_history_correct JOIN v_question_history_false 
    ON v_question_history_correct.question_id = v_question_history_false.question_id;

这就是我得到的 enter image description here

这是正确答案的内容 enter image description here

这是错误答案的内容 enter image description here

如有任何帮助，我们将不胜感激。添加我对 JOIN 内容还是新的，所以我可能一开始就写了错误的语法。谢谢

编辑：两个答案都解决了谢谢大家我制作 View 的原因是为了以防万一我需要使用只有 true 或 false 的数据我可以只使用视图而不是完整 select。因为将来我会将该视图与另一个 table.

的数据结合起来

Answer 1

试试这个：

    SELECT coalesce(v_question_history_correct.question_id,f.question_id,v_question_history_false.question_id) 'question_id',true_answer,false_answer 
FROM v_question_history_correct 
    full JOIN v_question_history_false     ON v_question_history_correct.question_id = v_question_history_false.question_id;

Answer 2

您的数据

CREATE TABLE v_question_history_correct(question_id int ,true_answer  int);
insert into v_question_history_correct
(question_id,true_answer) VALUES 
(5,7),
(6,8),
(7,8);

CREATE TABLE v_question_history_false(question_id int ,false_answer   int);
insert into v_question_history_false
(question_id,false_answer ) VALUES 
(2,7),
(1,7),
(6,1),
(7,1);

使用 full join 相当于 mysql

SELECT VC.question_id,true_answer ,false_answer 
FROM v_question_history_correct VC
LEFT JOIN v_question_history_false  VF
    ON VC.question_id = VF.question_id;
UNION
SELECT VF.question_id,true_answer ,false_answer 
FROM v_question_history_correct VC
RIGHT JOIN v_question_history_false  VF
    ON VC.question_id = VF.question_id;

dbfiddle

SQL加入我想要的列的两倍

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