109 lines
3.0 KiB
SQL
109 lines
3.0 KiB
SQL
-- ========================================
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-- 添加外键约束 - 防止孤儿数据
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-- ========================================
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-- 作用：删除用户时自动级联删除学生相关数据
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-- 解决：课程分配人数 ≠ 用户管理人数的问题
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-- ========================================
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-- 第1步：检查当前是否有孤儿数据（应该已清理）
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SELECT
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'孤儿班级关联' AS type,
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COUNT(*) AS count
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FROM student_class sc
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LEFT JOIN sys_user u ON sc.student_id = u.user_id
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WHERE u.user_id IS NULL
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UNION ALL
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SELECT
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'孤儿课程分配' AS type,
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COUNT(*) AS count
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FROM course_assignment ca
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LEFT JOIN sys_user u ON ca.student_id = u.user_id
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WHERE u.user_id IS NULL;
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-- 如果有孤儿数据，先执行清理脚本！
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-- ========================================
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-- 第2步：添加外键约束
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-- ========================================
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-- 2.1 学生班级关联表
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ALTER TABLE student_class
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ADD CONSTRAINT fk_student_class_user
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FOREIGN KEY (student_id)
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REFERENCES sys_user(user_id)
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ON DELETE CASCADE; -- 删除用户时自动删除班级关联
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-- 2.2 课程分配表
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ALTER TABLE course_assignment
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ADD CONSTRAINT fk_assignment_student
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FOREIGN KEY (student_id)
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REFERENCES sys_user(user_id)
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ON DELETE CASCADE; -- 删除用户时自动删除课程分配
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-- 2.3 学习记录表
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ALTER TABLE learning_record
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ADD CONSTRAINT fk_learning_student
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FOREIGN KEY (student_id)
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REFERENCES sys_user(user_id)
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ON DELETE CASCADE; -- 删除用户时自动删除学习记录
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-- 2.4 学习记录详情表
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ALTER TABLE learning_detail
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ADD CONSTRAINT fk_detail_student
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FOREIGN KEY (student_id)
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REFERENCES sys_user(user_id)
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ON DELETE CASCADE;
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-- 2.5 考试记录表
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ALTER TABLE exam_record
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ADD CONSTRAINT fk_exam_student
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FOREIGN KEY (student_id)
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REFERENCES sys_user(user_id)
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ON DELETE CASCADE;
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-- 2.6 答题记录表
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ALTER TABLE student_answer
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ADD CONSTRAINT fk_answer_student
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FOREIGN KEY (student_id)
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REFERENCES sys_user(user_id)
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ON DELETE CASCADE;
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-- ========================================
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-- 第3步：验证外键约束
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-- ========================================
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SELECT
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TABLE_NAME,
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CONSTRAINT_NAME,
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REFERENCED_TABLE_NAME,
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DELETE_RULE
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FROM information_schema.key_column_usage
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WHERE table_schema = 'study'
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AND referenced_table_name = 'sys_user'
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AND constraint_name LIKE 'fk%';
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-- 应该显示所有刚添加的外键约束
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-- ========================================
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-- 第4步：测试外键约束
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-- ========================================
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-- 测试方法：
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-- 1. 创建一个测试用户
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-- 2. 给该用户分配班级、课程等
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-- 3. 删除该用户
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-- 4. 检查相关数据是否自动删除
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-- ========================================
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-- 使用说明
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-- ========================================
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-- 1. 先确认孤儿数据已清理（第1步）
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-- 2. 执行第2步添加外键约束
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-- 3. 执行第3步验证
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-- 4. 以后删除用户时，相关数据会自动删除
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-- 5. 不会再产生孤儿数据
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-- 6. 课程分配人数 = 用户管理人数
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-- ========================================
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