-- ==========================================
-- 题目格式修复 - 逐步执行
-- 请按照注释一步一步执行，不要一次性全部执行
-- ==========================================

-- ==========================================
-- 第1步：查看最近的考试（找到要修复的考试ID）
-- ==========================================
SELECT id, exam_name, create_time 
FROM exam 
ORDER BY id DESC 
LIMIT 10;

-- 执行后，找到你要修复的考试ID，记下来
-- 例如：id = 14

-- ==========================================
-- 第2步：查看该考试的题目（检查是否有问题）
-- ==========================================
-- 将下面的 14 替换成你的考试ID
SELECT 
    id,
    question_type,
    question_content,
    LEFT(options, 100) as options_preview,
    correct_answer
FROM question
WHERE exam_id = 14
ORDER BY id;

-- 如果看到 options 中有 "A. "、"B. " 这样的前缀，说明需要修复

-- ==========================================
-- 第3步：备份数据（必须执行！）
-- ==========================================
CREATE TABLE question_backup_20251205 AS 
SELECT * FROM question;

-- 验证备份是否成功
SELECT COUNT(*) as backup_count FROM question_backup_20251205;

-- ==========================================
-- 第4步：修复题目（核心步骤）
-- ==========================================
-- 将下面的 14 替换成你的考试ID
UPDATE question
SET 
    options = REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(
        options,
        '"A. ', '"'),
        '"B. ', '"'),
        '"C. ', '"'),
        '"D. ', '"'),
        '"E. ', '"'),
        '"F. ', '"'),
    correct_answer = CASE 
        WHEN correct_answer LIKE 'A. %' THEN 'A'
        WHEN correct_answer LIKE 'B. %' THEN 'B'
        WHEN correct_answer LIKE 'C. %' THEN 'C'
        WHEN correct_answer LIKE 'D. %' THEN 'D'
        WHEN correct_answer LIKE 'E. %' THEN 'E'
        WHEN correct_answer LIKE 'F. %' THEN 'F'
        ELSE correct_answer
    END
WHERE exam_id = 14
  AND question_type IN ('single', 'multiple');

-- ==========================================
-- 第5步：验证修复结果
-- ==========================================
-- 将下面的 14 替换成你的考试ID
SELECT 
    id,
    question_content,
    options,
    correct_answer
FROM question
WHERE exam_id = 14
ORDER BY id;

-- 检查结果：
-- options 应该是: ["选项内容1","选项内容2"]  ✅
-- correct_answer 应该是: A  ✅

-- ==========================================
-- 第6步：检查学生答案（如果有人已经做过题）
-- ==========================================
-- 将下面的 14 替换成你的考试ID
SELECT 
    sa.id,
    sa.student_id,
    sa.question_id,
    sa.student_answer,
    q.correct_answer
FROM student_answer sa
JOIN question q ON sa.question_id = q.id
WHERE sa.exam_id = 14
ORDER BY sa.student_id, sa.question_id;

-- 如果 student_answer 也是 "A. 选项内容" 格式，执行下面的修复：
-- UPDATE student_answer
-- SET student_answer = CASE 
--     WHEN student_answer LIKE 'A. %' THEN 'A'
--     WHEN student_answer LIKE 'B. %' THEN 'B'
--     WHEN student_answer LIKE 'C. %' THEN 'C'
--     WHEN student_answer LIKE 'D. %' THEN 'D'
--     ELSE student_answer
-- END
-- WHERE exam_id = 14;

-- ==========================================
-- 完成！
-- ==========================================
-- 如果一切正常，修复完成
-- 如果出现问题，可以从备份恢复：
-- DELETE FROM question WHERE exam_id = 14;
-- INSERT INTO question SELECT * FROM question_backup_20251205 WHERE exam_id = 14;