帮助进行基本的 SQL 查询

Question

我为学校项目创建了一些表格。感兴趣的表是

                //table courses
        CREATE TABLE courses(courseId SERIAL PRIMARY KEY, facultyId REFERENCES faculties(facultyId), courseName TEXT);

                //table weights
    CREATE TABLE weights(weightId SERIAL PRIMARY KEY, weightName TEXT, weight INTEGER);

//table subjects
CREATE TABLE subjects(subjectId SERIAL PRIMARY KEY, subjectName TEXT);
        //table weights_subjects_courses
    CREATE TABLE weights_subjects_courses(courseId integer REFERENCES courses(courseId), weightId integer REFERENCES weights(weightId), subjectId integer REFERENCES subjects(subjectId)

当我尝试以下查询时出现问题

SELECT * FROM courses, subjects, weights WHERE courses.courseId= weights_subjects_courses.courseId AND subjects.subjectId= weights_subjects_courses.subjectId AND weights.weightId= weights_subjects_courses.weightId ORDER BY courseName;

，我收到此错误 SQL 错误：

ERROR:  missing FROM-clause entry for table "weights_subjects_courses"
LINE 1: ...ourses, subjects, weights WHERE courses.courseId= weights_su...
                                                             ^

提前致谢

Answer 1

您的 where 子句中有weights_subjects_courses，但它不在 from 子句中。每当您在 where 子句中连接表时，您还需要将它们包含在 from 子句中。

因此，只需将weights_subjects_courses 添加到您的from 子句中即可修复该错误。