mySql 学习总结

    今天基本完成了项目的模块的基本功能，剩下的就是对项目的吃透，对各种工具类的掌握，其中sql语句的书写就显得很重要了，特别是新的任务就是   写一个统计板块，sql语句基本从网上各大扒，基本已经成型，上没有完成的是对sql语句运行完之后得到的数据的封装并且转发给前端

            现总结今天的SQL函数

select sum(case when  sys_user.uName ='超级管理员' then 1 else 0 end) ,
          sum(case when  biz_order.uId = '21' then 1 else 0 end)  ,
          sum(case when  biz_order.uId = 'QiuZhiLinCeShi' then 1 else 0 end) 
from biz_order
LEFT JOIN sys_user ON sys_user.uId = biz_order.uId
WHERE year(biz_order.oAcceptanceDate)BETWEEN '2017' AND '2018'; 
group by biz_order.uId

     这是一个列转行的方式

select   
sum(case month(biz_order.oAcceptanceDate) when '1' then 1 else 0 end) as January,  
sum(case month(biz_order.oAcceptanceDate) when '2' then 1 else 0 end) as February,  
sum(case month(biz_order.oAcceptanceDate) when '3' then 1 else 0 end) as March,  
sum(case month(biz_order.oAcceptanceDate) when '4' then 1 else 0 end) as April,  
sum(case month(biz_order.oAcceptanceDate) when '5' then 1 else 0 end) as May,  
sum(case month(biz_order.oAcceptanceDate) when '6' then 1 else 0 end) as June, 
sum(case month(biz_order.oAcceptanceDate) when '7' then 1 else 0 end) as July,  
sum(case month(biz_order.oAcceptanceDate) when '8' then 1 else 0 end) as August,  
sum(case month(biz_order.oAcceptanceDate) when '9' then 1 else 0 end) as September,  
sum(case month(biz_order.oAcceptanceDate) when '10' then 1 else 0 end) as October,  
sum(case month(biz_order.oAcceptanceDate) when '11' then 1 else 0 end) as November,  
sum(case month(biz_order.oAcceptanceDate) when '12' then 1 else 0 end) as December  
from biz_order  
where year(biz_order.oAcceptanceDate)='2018'; 

以上就是我的项目涉及到的行转列的地方