USE study;

-- 1. 查看所有没有正确答案的题目
SELECT 
    id,
    question_type,
    LEFT(question_content, 40) AS content,
    correct_answer,
    CASE 
        WHEN correct_answer IS NULL OR correct_answer = '' THEN 'EMPTY'
        ELSE 'OK'
    END AS status
FROM question
WHERE correct_answer IS NULL OR correct_answer = ''
ORDER BY id;

-- 2. 查看题库中没有正确答案的题目
SELECT 
    id,
    bank_id,
    question_type,
    LEFT(question_content, 40) AS content,
    correct_answer,
    CASE 
        WHEN correct_answer IS NULL OR correct_answer = '' THEN 'EMPTY'
        ELSE 'OK'
    END AS status
FROM question_bank_item
WHERE correct_answer IS NULL OR correct_answer = ''
ORDER BY id;

-- 3. 统计有问题的题目数量
SELECT 
    '考试题目' AS source,
    question_type,
    COUNT(*) AS count
FROM question
WHERE correct_answer IS NULL OR correct_answer = ''
GROUP BY question_type

UNION ALL

SELECT 
    '题库题目' AS source,
    question_type,
    COUNT(*) AS count
FROM question_bank_item
WHERE correct_answer IS NULL OR correct_answer = ''
GROUP BY question_type;

-- 4. 对于多选题，如果答案为空，可以设置一个默认值（需要手动确认）
-- 警告：这会修改数据，请先备份！
-- UPDATE question 
-- SET correct_answer = 'A'
-- WHERE question_type = 'multiple' 
--   AND (correct_answer IS NULL OR correct_answer = '')
--   AND id IN (具体的ID);

-- 5. 查看特定考试的题目答案情况
SELECT 
    q.id,
    e.exam_name,
    q.question_type,
    LEFT(q.question_content, 30) AS content,
    q.correct_answer
FROM question q
LEFT JOIN exam e ON q.exam_id = e.id
WHERE e.exam_name LIKE '%Test%'
ORDER BY q.exam_id, q.id;