从品牌网站建设到网络营销策划,从策略到执行的一站式服务
学生表student(id,name)
老师表teacher(id,name)
课程表lesson(id,name)
老师和课程关联表(id,teacher_id,lesson_id)
学生和课程关联表(id,student_id,lesson_id)
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查询王老师的课程
SELECT t.name AS '老师',l.name AS '课程' FROM teacher t
LEFT JOIN teacher_lesson teal ON t.id = teal.teacher_id
LEFT JOIN lesson l ON l.id = teal.lesson_id WHERE t.name = '王老师'
查询上了王老师或张老师课的学生
SELECT s.name AS '学生',l.name AS '课程',t.name AS '老师' FROM student s
LEFT JOIN student_lesson stul ON s.id = stul.student_id
LEFT JOIN lesson l ON l.id = stul.lesson_id
LEFT JOIN teacher_lesson teal ON teal.lesson_id = l.id
LEFT JOIN teacher t ON t.id = teal.teacher_id WHERE t.name = '王老师' OR t.name = '张老师'
查询即上王老师又上张老师课的学生
SELECT * FROM student s WHERE EXISTS (
SELECT 1 FROM teacher_lesson tl JOIN teacher t ON tl.teacher_id = t.id
JOIN student_lesson sl ON sl.lesson_id = tl.lesson_id WHERE sl.student_id = s.id AND t.name = '王老师'
) AND EXISTS (
SELECT 1 FROM teacher_lesson tl JOIN teacher t ON tl.teacher_id = t.id
JOIN student_lesson sl ON sl.lesson_id = tl.lesson_id WHERE sl.student_id = s.id AND t.name = '张老师'
);
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