mysql tips

[奇巧淫技]

mysql可以不写group by直接使用having 等价于 group by null having

group by null 等价于 limit 1

因此直接having 等价于 limit 1 having

http://www.penglixun.com/tech/database/having_without_groupby_in_mysql.html

[真枪实弹]

mysql数据类型介绍(date, timestamp, int, varchar需要单独总结)

http://pansj89.blog.163.com/blog/static/991062192011846132930/