如何从一个表中获取另一表中不存在的行

Posted 2023-03-27

【中文标题】如何从一个表中获取另一表中不存在的行

【英文标题】：How do I get rows from one table that do not exist in another table

【发布时间】：2017-12-02 23:53:03

【问题描述】：

我正在使用下表 DDL 构建一个 Spring Boot 应用程序

CREATE TABLE IF NOT EXISTS QUESTIONS(
   question_id bigint auto_increment,
   question_text varchar(256),
   answer boolean, primary key(question_id)
);

CREATE INDEX IF NOT EXISTS question_id_index on Questions(question_id);

和

CREATE TABLE IF NOT EXISTS QuizQuestions(
    id bigint auto_increment,
    quiz_id varchar(10),
    question_id bigint,
    FOREIGN KEY(quiz_id) REFERENCES Quiz(quiz_id),
    FOREIGN KEY(question_id) REFERENCES Questions(question_id)
)

我需要写一个这样的sql查询

1) 如果QuizQuestions 表中至少存在一行quiz_id，那么我需要返回Questions 表中不存在于QuizQuestions 表中的所有question_id 条目.

2) 如果QuizQuestions 表中没有特定测验ID 的任何行，那么我想返回Questions 表中的所有行。

我的样本数据如下

INSERT INTO Questions(question_id, question_text, answer) VALUES (1, 'Is 2016 a leap year?', TRUE);
INSERT INTO Questions(question_id, question_text, answer) VALUES(2, 'Is Sunday a weekday?', FALSE);
INSERT INTO Questions(question_id, question_text, answer) VALUES(3, 'Is August the 8th month?', TRUE);
INSERT INTO Questions(question_id, question_text, answer) VALUES(4, 'Is July 25 independence day of United States of America?', FALSE);
INSERT INTO Questions(question_id, question_text, answer) VALUES(5, 'Does January have 31 days in a month?', TRUE);
INSERT INTO Questions(question_id, question_text, answer) VALUES(6, 'Does UK have a monarchy?', TRUE);
INSERT INTO Questions(question_id, question_text, answer) VALUES(7, 'Does Lebron play football?', FALSE);
INSERT INTO Questions(question_id, question_text, answer) VALUES(8, 'Is Los Angeles in New York state?', FALSE);
INSERT INTO Questions(question_id, question_text, answer) VALUES(9, 'Is Canada to the north of United States?', TRUE);
INSERT INTO Questions(question_id, question_text, answer) VALUES(10, 'Does November have 30 days in a month?', TRUE);

和

INSERT INTO QuizQuestions(quiz_id, question_id) VALUES('ABCDE12345', 5);

所以如果我查询quiz_id = ABCDE12345，我想从Questions 返回所有行，除了question_id=5 的条目，因为它已经存在于QuizQuestions 表中。

如果我要查询QuizQuestions 表中不存在的任何其他测验ID，那么我想返回Question 表中的所有条目。这是我的示例查询

SELECT q.question_id, q.question_text, q.answer FROM Questions q
LEFT JOIN QuizQuestions qq ON q.question_id = qq.question_id WHERE 
qq.quiz_id = ?

和

SELECT q.question_id, q.question_text, q.answer FROM Questions q 
LEFT JOIN QuizQuestions qq ON 
q.question_id = qq.question_id WHERE q.question_id NOT IN 
(SELECT qq.question_id FROM Questions WHERE qq.quiz_id = ?)

我已经尝试了我能想到的所有可能的查询，但我无法找到输出。

更新

这是我用来查询数据库的代码。集合输出始终为空。

public QuizQuestion fetchUniqueQuizQuestion(String quizId) 
    StringBuilder sb = new StringBuilder();
    sb.append("SELECT q.question_id, q.question_text, q.answer FROM Questions q ");
    sb.append("WHERE NOT EXISTS (SELECT 1 FROM QuizQuestions WHERE question_id = q.question_id ");
    sb.append(" AND quiz_id = ?) ");
    sb.append("OR NOT EXISTS (SELECT 1 FROM QuizQuestions WHERE quiz_id = ?)");
    List<QuizQuestion> questions = 
        this.jdbcTemplate.query(
            sb.toString(), new Object[] quizId, quizId, new RowMapper<QuizQuestion>() 

          @Override
          public QuizQuestion mapRow(ResultSet rs, int rowNum) throws SQLException 
            QuizQuestion qq = new QuizQuestion();
            qq.setQuestionId(rs.getInt("question_id"));
            qq.setQuizId(quizId);
            qq.setAnswer(rs.getBoolean("answer"));
            qq.setDescription(rs.getString("question_text"));
            return qq;
          
        );
    Collections.shuffle(questions);
    return questions.isEmpty() ? null : questions.get(0);
  

【参考方案1】：

类似：

SELECT q.question_id, q.question_text, q.answer 
FROM Questions q
WHERE NOT EXISTS 
    (
        SELECT 1 
        FROM QuizQuestions 
        WHERE question_id = q.question_id
            AND
            quiz_id = 'the_quiz_id'
    )
    OR 
    NOT EXISTS
    (
        SELECT 1 
        FROM QuizQuestions 
        WHERE quiz_id = 'the_quiz_id'
    )

【讨论】：

我不明白这个查询。你介意解释一下吗？

如果问题与指定 quiz_id 的 QuizQuestion 不匹配，则第一个 NOT EXISTS 将返回 true。如果指定的 quiz_id 没有 QuizQuestions，则第二个 NOT EXISTS 返回 true

我在测试模式下运行了查询，但它对我不起作用。

@Kartik - “不起作用”不是一个充分的描述。更加详细一些。你有错误吗？如果是这样，它是什么？你得到错误的结果吗？如果是这样，你得到什么与你期望什么？您可能应该edit your question 提供更多信息。

您好，结果集没有返回任何响应。我得到一个空列表。更新了我的帖子。