SQL從Access中的兩個不同表中減去值

Question

我有兩個不同的表，每個表包含一個值。例如：

table1    table2 

|Hours_worked|  |Work_Completed| 
    250     346 

我想要我的查詢從Work_completed中減去Hours_worked。我嘗試這樣做：

SELECT (SELECT Hours_worked FROM table1)- (SELECT Work_Completed FROM table2) AS Diff 

我得到的錯誤：「查詢輸入必須包含至少一個表或查詢」

任何幫助將是巨大的，感謝

Answer 1

我覺得這純粹是：

select Hours_worked - Work_Completed as diff 
from table1, table2 

Answer 2

只需添加FROM雙，我的意思是：

SELECT 
(SELECT Hours_worked FROM table1) - (SELECT Work_Completed FROM table2) AS Diff 
FROM DUAL