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简介 删除emp_no重复的记录，只保留最小的id对应的记录。 DELETE FROM titles_test where id not in( select * from( select MIN(id) from titles_test group by emp_no )as a ) 阅读全文
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简介 修改数据 update titles_test set emp_no = replace(emp_no, 10001, 10005) where id = 5; update titles_test set to_date = NULL, from_date ='2001-01-01' whe 阅读全文
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简介 alter table titles_test rename to titles_2017; 阅读全文
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简介 having 的使用考察 select number from grade group by number having count(number) >= 3; 阅读全文
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简介 left join select a.id, a.name, b.content from person as a left join task as b on b.person_id = a.id order by a.id; 阅读全文
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简介 简单 select user_id, max(date) from login group by user_id order by user_id; 阅读全文
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简介 使用 round 与 avg select job, round(avg(score),3) as avg from grade group by job order by avg desc; 阅读全文
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简介 使用 多个 and 并列 select * from order_info where date > "2025-10-15" and status = "completed" and product_name in("C++","Java","Python") order by id; 阅读全文
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简介 select job, sum(num) as cnt from resume_info where resume_info.date < '2026-01-01' and resume_info.date >= '2025-01-01' group by job order by cnt d 阅读全文
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简介 order by 然后 limit select * from employees order by hire_date desc limit 1; 阅读全文