MySql常见易错点分析

left join 左关联查询

select *, b.id as child_id, b.sequ as child_sequ from question a 
left join question_detail b on a.id=b.question_id 
where q.id='hagjhfhsjk' order by b.sequence;

order by 排序

降序：

order by 列名 desc;

升序：

order by 列名;
order by 列名 asc;

order by 语句必须放在整个sql的最后

delete 删除

delete from 表名;//注意：delete和from中间没有*

select 选择

注意是否需要加筛选条件：

where del_flag=1

update 修改

update 表名 set 列名A=值A, 列名B=值B where ×××;

注意：值B后边没有逗号

like 模糊查询

用法：

where column like '小%';
where column not like '小%';

默认不区分大小写