Question

我有3个表=＆＃39;测试＆＃39;，＆＃39;测试＆＃39;，＆＃39;主题＆＃39;

表格测试

idtest | Test
1      | Test wave 1
2      | Test Wave 2

表格测试

idtest | idsubject
1      | 1
1      | 2
1      | 3
2      | 1

表主题

  idsubject| subject
    1      | Math
    2      | Bio
    3      | Sport
    4      | Literature

我需要的是选择外部（某些测试中未选择的主题），例如，在idtest = 1上，结果将是文献

 idsubject | subject
    4      | Literature

不知何故，我已经尝试过使用left，outer didn＆work，而不是结果（选择/选择）主题。

SELECT subject.idsubject, subject FROM subject right OUTER JOIN test_quo ON (subject.idsubject = test_quo.idsubject) where test_quo.idtest=1'

查询我会得到结果

idsubject | subject
       1  | Math
       2  | Bio
       3  | Sport

Answer 1

我相信你需要下面的东西。它会给你＆＃34;未被选中＆＃34;所有测试的科目。

ParseQuery<ParseObject> roomQuery = ParseQuery.getQuery("Room");
        roomQuery.whereEqualTo("course" , courseName);
        roomQuery.whereEqualTo("number" , Integer.parseInt(courseNumber));

DEMO

仅针对SELECT subject.idsubject, subject FROM subject LEFT OUTER JOIN test_quo ON (subject.idsubject = test_quo.idsubject) WHERE ISNULL(test_quo.idsubject)我想出了以下相关的子查询：

idtest=1

Another Demo

和（最后）和OUTER JOIN相同：

SELECT s.idsubject, subject 
FROM subject s
WHERE NOT EXISTS (SELECT 1 
                  FROM test_quo t 
                  WHERE s.idsubject = t.idsubject AND t.idtest = 1)

Demo with one more subject

在assosiative表上的mysql外连接（未选中）

1 个答案: