ORACLE分组查询和统计等

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>加别名

2.子查询引用只能在查询出的结果中引用，比如子查询没有查出flow_id,外层不能用，另外外层不能引用内层的t

3.薪水前三名，内层查出薪水 order desc的虚表外层使用rownum<3

4.merge可以实现存在数据就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 可以查询出一组树的数据,注意最后connect by的条件（父节点=子节点向上查询反之向下查询）

可以order排序，可以加入两棵树（or），也可以加入where条件

select * from emp

where......

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

connect by prior mgr = empno

order by ...

6 份额（查询某数据占有总数据的百分比）

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

7 连续求和(同名分为同组累加)

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

8.带条件的连续求和（分部门连续求和）

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

9.分部门总和（取出orderby）

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

10工资的分组查询份额（总数的百分比）带上部门分组

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

注意这里查询的是“”分组“，因此这里查询的是变成一组为一个100%，查询的是一个部门中员工在本部分所占用的薪水比例

11分组查询出单一条件并分级（查询某一个部门的薪水的级别）注意rank()和row_number()的区别 rank是跳跃性并列(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“总”。。。。。。这个字眼一般使用group by（区分于over（partition by order by））

按部门分组查询部门的总薪水

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

13 总的基础上再次分组 group by + rollup

select sum(t.sal),t.deptno from emp t group by rollup (t.deptno)汇总后将总和进行求和

select sum(t.sal),t.job,t.deptno from emp t group by rollup (t.deptno,t.job)注意多个rollup其实只有第一个参数有效

14cube 连接在order by后面（代替ROLLUP） rollup升级版全部分组

15grouping实现不用java代码就可以对oracle 查询出的null字段进行赋值 0 本身结果 1合计结果

select sum(t.sal),t.deptno,
(case
when((grouping(t.job)=1 and grouping(t.deptno)=0)) then '部门小计'
when((grouping(t.job)=1 and grouping(t.deptno)=1)) then '部门总计'
else t.job end) as
job from emp t group by rollup (t.deptno,t.job)

16分组后的字段累加(比如按照员工名称，根据月份分组，实现自1月份到12月份工资累加，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分组最高值最低值平均值使用 max() over(partition by order by)代替sum() 还可以用min() avg()

18select * from v$transaction 查看事务

19多层分组函数和子查询之间的冲突问题

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

　　外层查询和内层分组冲突

--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 注意本条select中的分组和子查询都不可以作为函数的参数传入

巴特西

ORACLE分组查询和统计等

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