Как вычесть два столбца в SQL представлены в разных таблицах

Question

Update TotalItems 
set TotalItems.No_Items_Present = TotalItems.Total_Items - ItemsTable.No_Of_Items 
where TotalItems.Item_Name = ItemsTable.Item_Name

Мой запрос не работает. Любое решение ????

Answer 1

В MySQL вы бы сделали что-то вроде этого:

UPDATE TotalItems t, ItemsTable i
SET t.No_Items_Present = t.Total_Items - i.No_Of_Items
WHERE t.Item_Name = i.Item_Name

Answer 2

В MS SQL:

update ttl 
set No_Items_Present = ttl.Total_Items - itm.No_Of_Items 
from TotalItems ttl
    join ItemsTable itm on
        ttl.Item_Name = itm. Item_Name

В MySQL:

update TotalItems ttl
    join ItemsTable itm on
        ttl.Item_Name = itm. Item_Name
set tt1.No_Items_Present = ttl.Total_Items - itm.No_Of_Items 

Answer 3

update(
select ti.no_items_present,
       ti.total_items,
       it.no_of_items
   from total_items ti inner join
       itemstable it on ti.item_name=it.item_name)
set no_items_present=total_items-no_of_items

Answer 4

Попробуйте это:

UPDATE a SET a.No_Items_Present = a.Total_Items - b.No_Of_Items
FROM TotalItems a INNER JOIN ItemsTable b ON a.Item_Name = b.Item_Name