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-- 1. 删除活动报名记录
-- 需求：删除用户 ID 为 5 报名的所有活动。
DELETE FROM activity_sign
WHERE user_id = 5 ;
-- 2. 删除特定用户的评论
-- 需求：删除用户 ID 为 8 所有的评论记录。（ ， ）
DELETE FROM comment
WHERE user_id = 8 ;
-- 3. 删除过期的活动
-- 需求：删除所有结束时间在当前时间之前的活动。
DELETE FROM activity
WHERE end < NOW ( ) ;
-- 4. 删除无效的博客
-- 需求：删除所有浏览量为 0 且发布日期超过 1 年的博客。
DELETE FROM blog
WHERE read_count = 0 AND date < NOW ( ) - INTERVAL 1 YEAR ;
-- 5. 删除发布人ID为2的活动
-- 需求：
DELETE FROM activity
WHERE publisher_id = 2 ;
-- 6. 删除特定博客分类下的所有博客
-- 需求：删除分类为 "深海探险" 的所有博客。
DELETE FROM blog
WHERE category_id = ( SELECT id FROM category WHERE name = ' 深海探险 ' ) ;
-- 7. 删除评论中的指定内容
-- 需求：删除所有评论内容包含敏感词 "禁止" 的评论。
DELETE FROM comment
WHERE content LIKE ' %非常% ' ;
-- 8. 删除用户的数据
-- 需求：删除用户名为 testuser 的用户及其相关数据（包括博客、评论、收藏）。
DELETE FROM blog
WHERE user_id = ( SELECT id FROM user WHERE username = ' testuser ' ) ;
DELETE FROM comment
WHERE user_id = ( SELECT id FROM user WHERE username = ' testuser ' ) ;
DELETE FROM collect
WHERE user_id = ( SELECT id FROM user WHERE username = ' testuser ' ) ;
DELETE FROM user
WHERE username = ' testuser ' ;
-- 9. 删除过期的收藏记录
-- 需求：删除所有收藏的活动或博客，如果它们对应的活动或博客已经被删除。
DELETE FROM collect
WHERE ( fid , module ) NOT IN ( SELECT id , ' activity ' FROM activity UNION SELECT id , ' blog ' FROM blog ) ;
-- 10. 删除不活跃的用户
-- 需求：删除没有任何活动（报名、评论等）的用户数据。
DELETE FROM user
WHERE id IN (
SELECT id
FROM (
SELECT u . id
FROM user u
LEFT JOIN activity_sign a ON u . id = a . user_id
LEFT JOIN comment c ON u . id = c . user_id
WHERE a . user_id IS NULL OR c . user_id IS NULL
) AS temp_ids
) ;
