我可以爲子查詢創建別名嗎，以便我可以在其他子查詢中使用別名？

Question

我有一個冗長的oracle SQL腳本，它使用了幾個子查詢。如果我想使用相同的子查詢作爲另一個計算的一部分，我是否可以避免重複子查詢腳本？在下面的更小的腳本中，我可以給'onhand_uk'子查詢一個別名，所以我只能在'running_stock_UK'子查詢中使用別名？

select distinct 
    trunc(al.date_required) date_allocated, 
    al.component_part, al.qty_required, 
    sum(al.qty_required) over (partition by al.component_part order by trunc(al.date_required), al.component_part) running_demand_UK, 
    (select sum(pl.qty_onhand) 
    from part_loc pl 
    where al.component_part = pl.part_no and pl.plant in ('W','2') and pl.location_type = 'IN') onhand_UK, 
    (select sum(pl.qty_onhand) 
    from part_loc pl 
    where al.component_part = pl.part_no and pl.plant in ('W','2') and pl.location_type = 'IN') - sum(al.qty_required) over (partition by al.component_part order by trunc(al.date_required), 
    al.component_part) running_stock_UK 
from 
    allocations al, part_description pd 
where 
    al.alloc_plant = 'W' 
    and al.status_code between '4' and '8' 
    and al.component_part like 'Y%' 
    and al.component_part = 'Y450569' 
    and al.component_part = pd.part_no 
    and substr(pd.prodtyp,1,2) in ('JC','KT','TR') 
order by 
    al.component_part, trunc(al.date_required) 

非常感謝您的幫助。

Answer 1

和Dan Bracuk一樣，雖然你也在尋找WITH statement，但我查看了你的查詢，在這種情況下，我只是將所有東西都移到子查詢中，然後將減法運算放到main查詢：

select 
    x.date_allocated, 
    x.component_part, 
    x.qty_required, 
    x.running_demand_UK, 
    x.onhand_UK, 
    x.running_demand_UK - x.onhand_UK as running_stock_UK 
from 
    (select distinct 

     trunc(al.date_required) date_allocated, 
     al.component_part, al.qty_required, 

     sum(al.qty_required) over (
      partition by al.component_part 
      order by trunc(al.date_required), al.component_part) running_demand_UK, 

     (select sum(pl.qty_onhand) from part_loc pl 
     where al.component_part = pl.part_no 
      and pl.plant in ('W','2') 
      and pl.location_type = 'IN') onhand_UK 

    from allocations al, part_description pd 

    where al.alloc_plant = 'W' 
     and al.status_code between '4' and '8' 
     and al.component_part like 'Y%' 
     and al.component_part = 'Y450569' 
     and al.component_part = pd.part_no 
     and substr(pd.prodtyp,1,2) in ('JC','KT','TR')) x 
order by 
    x.component_part, 
    x.date_allocated