题解 | #删除记录（二）#

delete from  exam_record 
where submit_time is null or timestampdiff(minute,start_time,submit_time)<5
order by start_time
limit 3

该题有两个知识点:

• delete的语法.
• delete的执行顺序

delete的语法:

• 根据条件删除

delete from tb_name
where (条件...)
order by ..
limit...

• 全部删除（表清空，包含自增计数器重置）：

truncate tb_name

delete的执行顺序:from-->where--->order by-->limit-->delete