SQL查詢一年的十二個月份，形成報表

SELECT YEAR(日期欄位) 年度,SUM(CASE WHEN MONTH(日期欄位) =1 THEN 統計的欄位 ELSE 0 END) 一月,   
SUM(CASE WHEN MONTH(日期欄位) =2 THEN 統計的欄位 ELSE 0 END) 二月,
SUM(CASE WHEN MONTH(日期欄位) =3 THEN 統計的欄位 ELSE 0 END) 三月,
SUM(CASE WHEN MONTH(日期欄位) =4 THEN 統計的欄位 ELSE 0 END) 四月,
SUM(CASE WHEN MONTH(日期欄位) =5 THEN 統計的欄位 ELSE 0 END) 五月,
SUM(CASE WHEN MONTH(日期欄位) =6 THEN 統計的欄位 ELSE 0 END) 六月,
SUM(CASE WHEN MONTH(日期欄位) =7 THEN 統計的欄位 ELSE 0 END) 七月,
SUM(CASE WHEN MONTH(日期欄位) =8 THEN 統計的欄位 ELSE 0 END) 八月,
SUM(CASE WHEN MONTH(日期欄位) =9 THEN 統計的欄位 ELSE 0 END) 九月,
SUM(CASE WHEN MONTH(日期欄位) =10 THEN 統計的欄位 ELSE 0 END) 十月,
SUM(CASE WHEN MONTH(日期欄位) =11 THEN 統計的欄位 ELSE 0 END) 十一月,
SUM(CASE WHEN MONTH(日期欄位) =12 THEN 統計的欄位 ELSE 0 END) 十二月,
    FROM 表

        GROUP BY YEAR(日期欄位)

Oracle統計某一年中的1-12個月的資料總和

實戰案例

查詢2015年1月到12個月的所有實有人口數量和往年2014年1月到12個月的實有人口數量，沒有的月份顯示 人口數量為0.類似效果如圖

建立表

create table PERSONSITUATION
(
  id    NUMBER not null,
  rdate DATE,
  nums  NUMBER
)

插入資料

insert into PERSONSITUATION (id, rdate, nums) values (1, to_date('26-01-2015', 'dd-mm-yyyy'), 131);
insert into PERSONSITUATION (id, rdate, nums) values (2, to_date('27-01-2013', 'dd-mm-yyyy'), 232);
insert into PERSONSITUATION (id, rdate, nums) values (3, to_date('18-10-2013', 'dd-mm-yyyy'), 222);
insert into PERSONSITUATION (id, rdate, nums) values (4, to_date('20-01-2015', 'dd-mm-yyyy'), 232);
insert into PERSONSITUATION (id, rdate, nums) values (5, to_date('28-01-2015', 'dd-mm-yyyy'), 422);
insert into PERSONSITUATION (id, rdate, nums) values (6, to_date('26-02-2015', 'dd-mm-yyyy'), 232);
insert into PERSONSITUATION (id, rdate, nums) values (7, to_date('29-01-2014', 'dd-mm-yyyy'), 225);
insert into PERSONSITUATION (id, rdate, nums) values (8, to_date('31-01-2015', 'dd-mm-yyyy'), 111);
insert into PERSONSITUATION (id, rdate, nums) values (9, to_date('25-01-2013', 'dd-mm-yyyy'), 211);
insert into PERSONSITUATION (id, rdate, nums) values (10, to_date('25-01-2013', 'dd-mm-yyyy'), 251);
insert into PERSONSITUATION (id, rdate, nums) values (11, to_date('25-01-2013', 'dd-mm-yyyy'), 262);
insert into PERSONSITUATION (id, rdate, nums) values (12, to_date('25-08-2015', 'dd-mm-yyyy'), 233);
insert into PERSONSITUATION (id, rdate, nums) values (13, to_date('25-01-2013', 'dd-mm-yyyy'), 211);
insert into PERSONSITUATION (id, rdate, nums) values (14, to_date('25-02-2014', 'dd-mm-yyyy'), 222);
insert into PERSONSITUATION (id, rdate, nums) values (15, to_date('25-03-2012', 'dd-mm-yyyy'), 209);
insert into PERSONSITUATION (id, rdate, nums) values (16, to_date('25-01-2012', 'dd-mm-yyyy'), 219);

常見的統計中如下Sql語句，只查詢到了資料中有的月，如果沒有就什麼也沒有顯示，和明顯不符合1-12個月的12條資料統計

select to_char(rdate,'yyyy-mm') rdate,sum(nums) nums from personsituation where to_char(rdate,'yyyy')='2015' group by to_char(rdate,'yyyy-mm') order by rdate

正確的分析是：必須是12條資料，而且是統計的結果的12條資料，從這裡入手編寫如下Sql語句，顯示12個列的統計資料，先查詢出一年的資料，然後再連線另外一條資料拼接

select sum(decode(to_char(rdate,'mm'),'01',nums,0)) nums01,sum(decode(to_char(rdate,'mm'),'02',nums,0)) nums02,
       sum(decode(to_char(rdate,'mm'),'03',nums,0)) nums03,sum(decode(to_char(rdate,'mm'),'04',nums,0)) nums04, 
       sum(decode(to_char(rdate,'mm'),'05',nums,0)) nums05,sum(decode(to_char(rdate,'mm'),'06',nums,0)) nums06,
       sum(decode(to_char(rdate,'mm'),'07',nums,0)) nums07,sum(decode(to_char(rdate,'mm'),'08',nums,0)) nums08,
       sum(decode(to_char(rdate,'mm'),'09',nums,0)) nums09,sum(decode(to_char(rdate,'mm'),'10',nums,0)) nums10,
       sum(decode(to_char(rdate,'mm'),'11',nums,0)) nums11,sum(decode(to_char(rdate,'mm'),'12',nums,0)) nums12
           from personsituation 
           where to_char(rdate,'yyyy')='2015'

而前端頁面顯示的結果有兩種可能性，一種是橫向展示，一種是縱向展示，可以使用下面的sql語句進行列轉行的轉換得到如下結果

select * from (
  select sum(decode(to_char(rdate,'mm'),'01',nums,0)) nums01,sum(decode(to_char(rdate,'mm'),'02',nums,0)) nums02,
     sum(decode(to_char(rdate,'mm'),'03',nums,0)) nums03,sum(decode(to_char(rdate,'mm'),'04',nums,0)) nums04, 
     sum(decode(to_char(rdate,'mm'),'05',nums,0)) nums05,sum(decode(to_char(rdate,'mm'),'06',nums,0)) nums06,
     sum(decode(to_char(rdate,'mm'),'07',nums,0)) nums07,sum(decode(to_char(rdate,'mm'),'08',nums,0)) nums08,
     sum(decode(to_char(rdate,'mm'),'09',nums,0)) nums09,sum(decode(to_char(rdate,'mm'),'10',nums,0)) nums10,
     sum(decode(to_char(rdate,'mm'),'11',nums,0)) nums11,sum(decode(to_char(rdate,'mm'),'12',nums,0)) nums12
         from personsituation 
         where to_char(rdate,'yyyy')='2015'
)  unpivot (sum2015 for years in (nums01,nums02,nums03,nums04,nums05,nums06,nums07,nums08,nums09,nums10,nums11,nums12) )

最後一步就是和往年的資料對比使用left join查詢

select A.years,A.SUM2015,B.SUM2014 from    
  (select * from (
    select sum(decode(to_char(rdate,'mm'),'01',nums,0)) nums01,sum(decode(to_char(rdate,'mm'),'02',nums,0)) nums02,
       sum(decode(to_char(rdate,'mm'),'03',nums,0)) nums03,sum(decode(to_char(rdate,'mm'),'04',nums,0)) nums04, 
       sum(decode(to_char(rdate,'mm'),'05',nums,0)) nums05,sum(decode(to_char(rdate,'mm'),'06',nums,0)) nums06,
       sum(decode(to_char(rdate,'mm'),'07',nums,0)) nums07,sum(decode(to_char(rdate,'mm'),'08',nums,0)) nums08,
       sum(decode(to_char(rdate,'mm'),'09',nums,0)) nums09,sum(decode(to_char(rdate,'mm'),'10',nums,0)) nums10,
       sum(decode(to_char(rdate,'mm'),'11',nums,0)) nums11,sum(decode(to_char(rdate,'mm'),'12',nums,0)) nums12
           from personsituation 
           where to_char(rdate,'yyyy')='2015'
  ) unpivot (sum2015 for years in (nums01,nums02,nums03,nums04,nums05,nums06,nums07,nums08,nums09,nums10,nums11,nums12) )) A
left join
  (select * from (
    select sum(decode(to_char(rdate,'mm'),'01',nums,0)) nums01,sum(decode(to_char(rdate,'mm'),'02',nums,0)) nums02,
       sum(decode(to_char(rdate,'mm'),'03',nums,0)) nums03,sum(decode(to_char(rdate,'mm'),'04',nums,0)) nums04, 
       sum(decode(to_char(rdate,'mm'),'05',nums,0)) nums05,sum(decode(to_char(rdate,'mm'),'06',nums,0)) nums06,
       sum(decode(to_char(rdate,'mm'),'07',nums,0)) nums07,sum(decode(to_char(rdate,'mm'),'08',nums,0)) nums08,
       sum(decode(to_char(rdate,'mm'),'09',nums,0)) nums09,sum(decode(to_char(rdate,'mm'),'10',nums,0)) nums10,
       sum(decode(to_char(rdate,'mm'),'11',nums,0)) nums11,sum(decode(to_char(rdate,'mm'),'12',nums,0)) nums12
           from personsituation 
           where to_char(rdate,'yyyy')='2014'
  ) unpivot (sum2014 for years in (nums01,nums02,nums03,nums04,nums05,nums06,nums07,nums08,nums09,nums10,nums11,nums12) )) B 
on A.years = B.years

實現與效果圖一樣的資料，可以將sql中的nums01...nums12改為1月...12月

select A.years,A.SUM1,B.SUM2 from    
  (select * from (
    select sum(decode(to_char(rdate,'mm'),'01',nums,0)) 一月,sum(decode(to_char(rdate,'mm'),'02',nums,0)) 二月,
       sum(decode(to_char(rdate,'mm'),'03',nums,0)) 三月,sum(decode(to_char(rdate,'mm'),'04',nums,0)) 四月, 
       sum(decode(to_char(rdate,'mm'),'05',nums,0)) 五月,sum(decode(to_char(rdate,'mm'),'06',nums,0)) 六月,
       sum(decode(to_char(rdate,'mm'),'07',nums,0)) 七月,sum(decode(to_char(rdate,'mm'),'08',nums,0)) 八月,
       sum(decode(to_char(rdate,'mm'),'09',nums,0)) 九月,sum(decode(to_char(rdate,'mm'),'10',nums,0)) 十月,
       sum(decode(to_char(rdate,'mm'),'11',nums,0)) 十一月,sum(decode(to_char(rdate,'mm'),'12',nums,0)) 十二月
           from personsituation 
           where to_char(rdate,'yyyy')= '2015'
  ) unpivot (sum1 for years in (一月,二月,三月,四月,五月,六月,七月,八月, 九月,十月,十一月,十二月) )) A
left join
  (select * from (
    select sum(decode(to_char(rdate,'mm'),'01',nums,0)) 一月,sum(decode(to_char(rdate,'mm'),'02',nums,0)) 二月,
       sum(decode(to_char(rdate,'mm'),'03',nums,0)) 三月,sum(decode(to_char(rdate,'mm'),'04',nums,0)) 四月, 
       sum(decode(to_char(rdate,'mm'),'05',nums,0)) 五月,sum(decode(to_char(rdate,'mm'),'06',nums,0)) 六月,
       sum(decode(to_char(rdate,'mm'),'07',nums,0)) 七月,sum(decode(to_char(rdate,'mm'),'08',nums,0)) 八月,
       sum(decode(to_char(rdate,'mm'),'09',nums,0)) 九月,sum(decode(to_char(rdate,'mm'),'10',nums,0)) 十月,
       sum(decode(to_char(rdate,'mm'),'11',nums,0)) 十一月,sum(decode(to_char(rdate,'mm'),'12',nums,0)) 十二月
           from personsituation 
           where to_char(rdate,'yyyy')= '2014'
  ) unpivot (sum2 for years in (一月,二月,三月,四月,五月,六月,七月,八月, 九月,十月,十一月,十二月) )) B 
on A.years = B.years