Question

美好的一天。

我有下表：

Order_Header（Order_id {pk}，customer_id {fk}，agent_id {fk}，Order_date（DATE FORMAT））
Invoice_Header（Invoice_ID {pk}，Customer_ID {fk}，Agent_ID {fk}，invoice_Date {DATE FORMAT}）
库存（Product_ID {pk}，Product_description）

我创建了一个名为 AVG_COMPLETION_TIME_FACT 的表，并希望使用与前3个表有关的以下值填充该表：

产品ID
发票月
发票年份
AVG_Completion_Time（发票日期-订单日期）

我有以下无效的代码：

    INSERT INTO AVG_COMPLETION_TIME_FACT(

SELECT PRODUCT_ID, EXTRACT (YEAR FROM INVOICE_DATE), EXTRACT (MONTH FROM INVOICE_DATE), (INVOICE_DATE - ORDER_DATE)
FROM STOCK, INVOICE_HEADER, ORDER_HEADER
GROUP BY PRODUCT_ID, EXTRACT (YEAR FROM INVOICE_DATE), EXTRACT (MONTH FROM INVOICE_DATE)
);

我想按product_id，发票年份和发票月份分组。

这可能吗？

任何建议将不胜感激。

致谢

Answer 1

简短的回答：有可能-如果您的数据库包含编写正确查询所需的更多列。

除了语法上的问题外，还有几个问题。当我们创建一些测试表时，您会发现所需的答案无法从问题中提供的列中得出。示例表（Oracle 12c），省略了所有PK / FK约束：

-- 3 tables, similar to the ones described in your question,
-- including some test data
create table order_header (id, customer_id, agent_id, order_date )
as
select 1000, 100, 1, date'2018-01-01' from dual union all
select 1001, 100, 2, date'2018-01-02' from dual union all
select 1002, 100, 3, date'2018-01-03' from dual
;

create table invoice_header ( id, customer_id, agent_id, invoice_date )
as
select 2000, 100, 1, date'2018-02-01' from dual union all
select 2001, 100, 2, date'2018-03-11' from dual union all
select 2002, 100, 3, date'2018-04-21' from dual
;

create table stock( product_id, product_description) 
as
select 3000, 'product3000' from dual union all
select 3001, 'product3001' from dual union all
select 3002, 'product3002' from dual
;

如果按照完成的方式联接表（使用交叉联接），则会看到比预期多的行...但是：invoice_header表和order_header表均不包含任何PRODUCT_ID数据。因此，我们无法确定哪些product_id与存储的order_id或invoice_id相关。

select 
  product_id
, extract( year from invoice_date )
, extract( month from invoice_date )
, invoice_date - order_date
from stock, invoice_header, order_header -- cross join -> too many rows in the resultset!
-- group by ...
;
...
27 rows selected.

为使查询正确，您可能应该编写INNER JOIN和条件（关键字：ON）。如果我们尝试使用您的原始表定义（如您的问题中所述）执行此操作，您将看到我们无法联接所有3个表，因为它们不包含所有需要的列：PRODUCT_ID（表STOCK）无法与ORDER_HEADER或INVOICE_HEADER。

这两个表（ORDER_HEADER和INVOICE_HEADER）的一个共同点是customer_id，但这不足以回答您的问题。但是，我们可以使用它来演示如何编写JOIN。

select 
  -- product_id
  IH.customer_id  as cust_id
, OH.id           as OH_id
, IH.id           as IH_id
, extract( year from invoice_date )  as year_
, extract( month from invoice_date ) as month_
, invoice_date - order_date          as completion_time
from invoice_header IH
  join order_header OH on IH.customer_id = OH.customer_id
-- the stock table cannot be joined at this stage
;

缺少列：请将以下内容视为“概念验证”代码。假设在数据库中的某个地方，您的表中的列具有{1}链接STOCK和ORDER_HEADER（此处为STOCK_ORDER）和{2}链接ORDER_HEADER和INVOICE_HEADER（此处为ORDER_INVOICE），则实际上可以获取所需的信息。

-- each ORDER_HEADER is mapped to multiple product_ids
create table stock_order
as
select S.product_id, OH.id as oh_id  -- STOCK and ORDER_HEADER
from stock S, order_header OH ; -- cross join, we use all possible combinations here


select oh_id, product_id 
from stock_order 
order by OH_id 
;

PRODUCT_ID      OH_ID
---------- ----------
      3000       1000
      3000       1001
      3000       1002
      3001       1000
      3001       1001
      3001       1002
      3002       1000
      3002       1001
      3002       1002

9 rows selected.

-- each INVOICE_HEADER mapped to a single ORDER_HEADER
create table order_invoice ( order_id, invoice_id )
as
select 1000, 2000 from dual union all
select 1001, 2001 from dual union all
select 1002, 2002 from dual
;

对于查询，请确保您编码了正确的JOIN条件（ON ...），例如

-- example query. NOTICE: conditions in ON ...
select 
  S.product_id
, IH.customer_id  as cust_id
, OH.id           as OH_id
, IH.id           as IH_id
, extract( year from invoice_date )  as year_
, extract( month from invoice_date ) as month_
, invoice_date - order_date          as completion_time
from invoice_header IH
  join order_invoice OI on IH.id = OI.invoice_id     -- <- new "link" table
  join order_header OH  on OI.order_id = OH.id  
  join stock_order SO   on OH.id = SO.OH_id          -- <- new "link" table
  join stock S          on S.product_id = SO.product_id 
;

现在，您可以添加GROUP BY，然后仅选择所需的列。与INSERT结合使用，您应该编写类似...

-- example avg_completion_time_fact table.  
create table avg_completion_time_fact (
  product_id number
, year_ number
, month_ number
, avg_completion_time number
) ;


insert into avg_completion_time_fact ( product_id, year_, month_, avg_completion_time )
select 
  S.product_id
, extract( year from invoice_date )  as year_
, extract( month from invoice_date ) as month_
, avg( invoice_date - order_date )   as avg_completion_time
from invoice_header IH
  join order_invoice OI on IH.id = OI.invoice_id
  join order_header OH  on OI.order_id = OH.id  
  join stock_order SO   on OH.id = SO.OH_id
  join stock S          on S.product_id = SO.product_id 
group by S.product_id, extract( year from invoice_date ), extract( month from invoice_date )  
;

AVG_COMPLETION_TIME_FACT表现在包含：

SQL> select * from avg_completion_time_fact order by product_id ;

PRODUCT_ID      YEAR_     MONTH_ AVG_COMPLETION_TIME
---------- ---------- ---------- -------------------
      3000       2018          3                  68
      3000       2018          4                 108
      3000       2018          2                  31
      3001       2018          3                  68
      3001       2018          2                  31
      3001       2018          4                 108
      3002       2018          3                  68
      3002       2018          4                 108
      3002       2018          2                  31

由于我们不知道数据库所包含的所有表的定义，因此尚不清楚数据库（或架构）的最终查询将是什么样。但是，如果应用这些技术并坚持使用示例的语法，则应该能够获得所需的结果。祝你好运！

从不同的表填充表

1 个答案: