[mymap]
markmap
Links
- https://markmap.js.org/
- [GitHub](https://github.com/gera2ld/markmap)
Related
- [coc-markmap](https://github.com/gera2ld/coc-markmap)
- [gatsb...
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Posted by
spike
on 2022-04-05
1、groupby用法：根据性别和学校来分组
sql
select
gender,university,
count(gender)as user_num,
avg(active_days_within_30) as avg_active_day,
avg(question_cnt) as avg_question_cnt
from
user_profi...
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Posted by
spike
on 2022-03-28
1、求平均数，保留小数用round函数，groupby分组 示例代码：
sql
SELECT
university,
round((count(question_id) / count(DISTINCT question_practice_detail.device_id)), 1) AS avg_answer_cnt
FROM
user_profile
J...
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Posted by
spike
on 2022-03-28
存储过程和事务
存储过程和函数很像，但和函数的区别就是函数有返回值，存储过程没有返回值，存储过程是很多的sql语句组成
事务具有原子性，里面是很多的sql语句，要不一次全部成功，要不执行失败开始回滚
1. -- alter table `test2` add column NAME CHAR -- 增加一列
2. -- create table test11 like t...
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Posted by
spike
on 2022-03-28
[https://segmentfault.com/a/1190000014117720](https://segmentfault.com/a/1190000014117720)
[https://blog.csdn.net/yifengchaoran/article/details/110334784](https://blog.csdn.net/yifengchaoran/art...
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Posted by
spike
on 2022-03-28
