一个有关报表统计的oracle统计语句

下面是分享的sql，sql并不是本人亲自写出来而是请别人帮忙编码，事后问起他为什么会写这么复杂的sql

给我的回答是：多写一点就会了，期待oracle的高级查询方面有所增强

decode的用法来自：http://blog.csdn.net/u010924897/article/details/47066937

小计的算法来自：http://blog.csdn.net/lqh4188/article/details/7597117

select dwmc,case when zymc is null then '系部各年级人数合计' else zymc end yname

,sum("2014") njone, sum("2015")njtwo, sum("2016")njthree,sum("2017")njfire,sum(allNum) allNum

from(

select dwmc,zymc,zydm

,(case when min(decode(xznj,'2014',yxnum,null)) is null then 0 else min(decode(xznj,'2014',yxnum,null)) end) as "2014"

,(case when min(decode(xznj,'2015',yxnum,null)) is null then 0 else min(decode(xznj,'2015',yxnum,null)) end) as "2015"

,(case when min(decode(xznj,'2016',yxnum,null)) is null then 0 else min(decode(xznj,'2016',yxnum,null)) end)as "2016"

,(case when min(decode(xznj,'2017',yxnum,null)) is null then 0 else min(decode(xznj,'2017',yxnum,null)) end)as "2017"

,sum(yxnum)  as allNum

FROM (select dw.mc dwmc,t.xznj,z.zydm,z.zymc,

sum(case sfzx when '1' then 1 else 0 end) yxnum

from T_BZKS t, T_BZKS_ZY z,t_dw dw

where t.sfzx = '1' and z.zydm = t.zydm

and z.szyxdm = dw.dm and t.sfzx is not null

and to_number(t.xznj) >= '2014'

group by z.zydm, z.zymc,t.xznj,dw.mc

order by t.xznj asc  

) GROUP BY zymc,zydm,dwmc

)

group by grouping sets ((dwmc, zymc), dwmc);