多層分組 != pre java代碼 from pex int base lec

select flow_id,rw from (select t.flow_id ,rownum as rw from apex_030200.wwv_flow_list_templates t) where rw >= 5


1.rownum只能用<如果使用>加別名

2.子查詢引用只能在查詢出的結果中引用，比如子查詢沒有查出flow_id,外層不能用，另外外層不能引用內層的t

3.薪水前三名，內層查出薪水 order desc的虛表外層使用rownum<3

4.merge可以實現存在數據就update不存在你就insert

merge into product a

using （select 1717 product_id, ‘002‘ req_no from dual b）

on (a.product_id = b.product.id and a.req_no = b.req.no)

when matched then

update set product name = ‘‘.....................

when not matched then

insert () values ()

5.start with connect by 可以查詢出一組樹的數據,註意最後connect by的條件（父節點=子節點 向上查詢 反之向下查詢）

可以order排序，可以加入兩棵樹（or），也可以加入where條件

select * from emp

where......

start with empnc = 7369 or empnc = 7204(註意不能用and )

connect by prior mgr = empno

order by ...

6 份額（查詢某數據占有總數據的百分比）

select t.empno,t.ename,t.sal,
100*round(sal/sum(sal) over(),5)
from emp t

7 連續求和(同名分為同組 累加)

select t.empno,t.ename,t.sal,
sum(sal) over(order by sal)
from emp t

8.帶條件的連續求和（分部門連續求和）

select t.empno,t.ename,t.sal,t.deptno,
sum(sal) over(partition by t.deptno order by sal)
from emp t

9.分部門總和（取出orderby）

select t.empno,t.ename,t.sal,t.deptno,
sum(sal) over(partition by t.deptno)
from emp t

10工資的分組查詢份額（總數的百分比）帶上部門分組

select t.empno,t.ename,t.sal,t.deptno,
100*round(sal/sum(sal) over (partition by t.deptno),4)
from emp t

註意這裏查詢的是“”分組“，因此這裏查詢的是變成一組為一個100%，查詢的是一個部門中員工在本部分所占用的薪水比例

11分組查詢出單一條件並分級（查詢某一個部門的薪水的級別）註意rank()和row_number()的區別 rank是跳躍性並列(1.1.3.3.5) row_number(1.2.3.4.5)

select t.*,ROW_NUMBER() over(partition by t.deptno order by t.sal desc) rank from emp t

12“總”。。。。。。這個字眼一般使用group by（區分於over（partition by order by））

按部門分組查詢部門的總薪水

select sum(t.sal),t.deptno from emp t group by t.deptno

13 總的基礎上再次分組 group by + rollup

select sum(t.sal),t.deptno from emp t group by rollup (t.deptno)匯總後將總和進行求和

select sum(t.sal),t.job,t.deptno from emp t group by rollup (t.deptno,t.job)註意多個rollup其實只有第一個參數有效

14cube 連接在order by後面（代替ROLLUP） rollup升級版 全部分組

15grouping實現不用java代碼就可以對oracle 查詢出的null字段進行賦值 0 本身結果 1合計結果

select sum(t.sal),t.deptno,
(case
when((grouping(t.job)=1 and grouping(t.deptno)=0)) then ‘部門小計‘
when((grouping(t.job)=1 and grouping(t.deptno)=1)) then ‘部門總計‘
else t.job end) as
job from emp t group by rollup (t.deptno,t.job)

16分組後的字段累加(比如按照員工名稱，根據月份分組，實現自1月份到12月份工資累加，即二月份是 1月 + 2月 。。)
select t.empno, t.ename, t.sal, sum(sal) over (partition by t.ename order by t.sal desc) from emp t

17分組最高值 最低值 平均值 使用 max() over(partition by order by)代替sum() 還可以用min() avg()

18select * from v$transaction 查看事務

19多層分組函數和子查詢之間的沖突問題

select   a.CREATOR, a.count_Sum ,b.full_name,b.dept_code,b.area_code from (    
select temp.c CREATOR,count(temp.c) as count_Sum from (  
select   
         t.ca,  
         c.lv,instr(t.ca, ‘,‘, 1, c.lv) + 1,  
         substr(t.ca,  
                instr(t.ca, ‘,‘, 1, c.lv) + 1,  
                instr(t.ca, ‘,‘, 1, c.lv + 1) -  
                (instr(t.ca, ‘,‘, 1, c.lv) + 1)) AS c  
    from (select   
                 ‘,‘ || checker || ‘,‘ AS ca,  
                 checker,  
                 LENGTH(checker),  
                 length(checker || ‘,‘),  
                 REPLACE(checker, ‘,‘),  
                 length(REPLACE(checker, ‘,‘)),   
                 nvl(length(REPLACE(checker, ‘,‘)), 0),   
                 length(checker || ‘,‘) - nvl(length(REPLACE(checker, ‘,‘)), 0) AS cnt   
            FROM wm_time_info a where a.check_result !=1) t,  
         　　 (select LEVEL lv from dual CONNECT BY LEVEL <= 100) c  
   where c.lv <= t.cnt  ) temp group by temp.c) a ,base_user b where a.CREATOR = b.user_code  

　　外層查詢和內層分組沖突

--select   a.CREATOR, a.count_Sum ,b.full_name,b.dept_code,b.area_code from (    
select o.CREATOR,count(o.CREATOR) as count_Sum,FULLNAME,DEPTCODE,AREACODE from (  
select temp.c CREATOR,b.full_name FULLNAME,b.dept_code DEPTCODE,b.area_code AREACODE,work_date from  
(  
select   
         work_date,  
         t.ca,  
         c.lv,  
         instr(t.ca, ‘,‘, 1, c.lv) + 1,  
         substr(t.ca,  
                instr(t.ca, ‘,‘, 1, c.lv) + 1,  
                instr(t.ca, ‘,‘, 1, c.lv + 1) -  
                (instr(t.ca, ‘,‘, 1, c.lv) + 1)) AS c  
    from (  
    ---  
    select   
                 work_date,  
                 ‘,‘ || checker || ‘,‘ AS ca,  
                 checker,  
                 LENGTH(checker),  
                 length(checker || ‘,‘),  
                 REPLACE(checker, ‘,‘),  
                 length(REPLACE(checker, ‘,‘)),   
                 nvl(length(REPLACE(checker, ‘,‘)), 0),   
                 length(checker || ‘,‘) - nvl(length(REPLACE(checker, ‘,‘)), 0) AS cnt   
            FROM wm_time_info a where a.check_result !=1  
     ---         
            ) t,  
         　　 (select LEVEL lv from dual CONNECT BY LEVEL <= 100) c   
   where c.lv <= t.cnt   
   ) temp ,base_user b where temp.c = b.user_code ) o  
   --where work_date >=‘2016-01-10‘   
   group by o.CREATOR,FULLNAME,DEPTCODE,AREACODE  
   --) a ,base_user b where a.CREATOR = b.user_code  

　　20 註意 本條select中的分組和子查詢都不可以作為函數的參數傳入

ORACLE分組查詢和統計等