oracle sql 高级编程学习笔记（二十一)

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一、行求解顺序

select product, country, year, week, inventory, sale, receipts
  from sales_fact
 where country = 'Australia'
   and product = 'Xtend Memory' 
   model return updated rows 
   partition by(product, country)
   dimension by(year, week)
   measures(0 inventory, sale, receipts) rules automatic
   order(inventory [ year, week ] = nvl(inventory [ cv(year), cv(week) - 1 ], 0) - sale [ cv(year), cv(week) ] + receipts [ cv(year), cv(week) ])
 order by product, country, year, week;

对于列中求出每周的库存，我们把 automatic order 注释掉 ，
automatic order 允许数据库自动识别规则之间的依赖关系
会启用默认的排序sequential order 规则排序， 既rules中规则先后顺序
sql语句会报如下错误
ORA-32637: 顺序排序 MODEL 中的自循环规则

这是因为 代码inventory [ cv(year), cv(week) - 1 ]子句进行了跨行引用，库存列的值必须按照周的升序来进行计算，
例如 第二周的库存必须在得到第一周的库存值后才能进行计算。

当然除了使用 automatic order 我们也可以直接在规则进行排序

select product, country, year, week, inventory, sale, receipts
  from sales_fact
 where country = 'Australia'
   and product = 'Xtend Memory' 
   model return updated rows 
   partition by(product, country)
   dimension by(year, week)
   measures(0 inventory, sale, receipts) 
   rules /*automatic order*/
   (inventory [ year, week ]  order by year,week asc --通过order自己显示声明了行求解顺序
    = nvl(inventory [ cv(year), cv(week) - 1 ], 0) - sale [ cv(year), cv(week) ] + receipts [ cv(year), cv(week) ]

   ) 
 order by product, country, year, week;

二、规则求解顺序

select * from (select product, country, year, week, inventory, sale, receipts
  from sales_fact
 where country = 'Australia'
   and product = 'Xtend Memory'
     model return updated rows 
   partition by(product, country)
   dimension by(year, week)
   measures(0 inventory, sale, receipts) 
   rules sequential order
   (inventory [ year, week ] order by year,week asc   
    = nvl(inventory [ cv(year), cv(week) - 1 ], 0) - sale [ cv(year), cv(week) ] + receipts [ cv(year), cv(week) ]
    ,
    receipts[year in(2000,2001),week in (51,52,53)] 
        order by year ,week asc  -- 这里排序不能少  不然因为上面规则中涉及到跨行处理 不然还是会报 ORA-32637错误
=receipts[cv(year),cv(week)]*10
   ) 

 order by product, country, year, week)
 where week>50 --用于筛选修改的receipts，便于查看结果;

从结果中明显看到，先按照求解库存后，再重新计算收入receipts

三、聚合函数

select product, country, year, week, inventory, sale, receipts, avg_inventory, max_sale
  from sales_fact
 where country = 'Australia'
   and product = 'Xtend Memory'
     model return updated rows 
   partition by(product, country)
   dimension by(year, week)
   measures(0 inventory,0 avg_inventory,0 max_sale, sale, receipts) 
   rules  automatic order
   (inventory [ year, week ] 
    = nvl(inventory [ cv(year), cv(week) - 1 ], 0) - sale [ cv(year), cv(week) ] + receipts [ cv(year), cv(week) ]
    ,
    avg_inventory[year,any]=round(avg(inventory)[cv(year),week],2),
    max_sale[year,any]=max(sale)[cv(year),week]
   ) 

 order by product, country, year, week

avg_inventory[year, ANY] = avg(inventory)[cv(year) , week ]，用ANY是因为右侧的表达式对于所有的week都会返回相同的值，所以没必要重复计算，对于所有的week只需要计算一次就行了。Avg后面的[cv(year) , week ]表示聚合的范围是这一年和所有周。

四、迭代

1、实例演示

select  year, week, sale, sale_list
  from sales_fact
 where country = 'Australia'
   and product = 'Xtend Memory'
     model return updated rows 
   partition by(product, country)
   dimension by(year, week)
   measures( cast('' as varchar2(50))sale_list, sale ) 
   rules  iterate(5)-- 规则会迭代5次，ITERATION_NUMBER从0到4。
   ( sale_list[year,week] order by year,week asc=
    sale[cv(year),cv(week)-iteration_number+2]||--cv(week)-iteration_number+2 来访问前两周和后两周的数据
    case when iteration_number=0 then '' else ',' end||
-- case语句在为每个列表中除了第一个成员外每个成员都加上逗号。
      sale_list[cv(year),cv(week)]    
   ) 

 order by  year, week

同样这也是列转行 可以通过pivot函数实现

2、空值

语法
presentv(cell_reference,expr1,expr2)
表示 如果 cell_reference存在，则返回 expr1，不存在则返回expr2
PRESENTNNV（NOT NULL VALUE）
用法同PRESENTV，只是多了非空条件。
PRESENTNNV(t , v1 , v2) 如果单元格t存在且非空，返回v1，否则，返回v2。

接着示列中的例子

select  year, week, sale, sale_list
  from sales_fact
 where country = 'Australia'
   and product = 'Xtend Memory'
     model return updated rows 
   partition by(product, country)

   dimension by(year, week)
   measures( cast('' as varchar2(50))sale_list, sale ) 
   rules  iterate(5)
   ( sale_list[year,week] order by year,week asc=
   presentv(
     sale[cv(year),cv(week)-iteration_number+2],
     sale[cv(year),cv(week)-iteration_number+2]||
        case when iteration_number=0 then '' else ',' end||
         sale_list[cv(year),cv(week)],
      sale_list[cv(year),cv(week)] )  
   ) 

 order by  year, week

结果解决了 示列中存在双逗号问题。