從兩個表中減去派生列

Question

我有兩張表，seet和費用，我需要選擇從費用中支付的總額並從支付中減去它。

我試了下面的查詢，任何人都可以糾正它嗎？

我得到這個錯誤：

every derived table must have its own alias

SELECT (payable - pay) as balance 
FROM  (SELECT sum(paid) AS pay 
      FROM fees 
      WHERE adm = '5685') 
      UNION ALL 
      SELECT payable 
      FROM seet 
      WHERE term = 'term1') 
     )as t1 

Answer 1

SELECT (SELECT payable FROM seet WHERE term = 'term1') - 
     (SELECT sum(paid) FROM fees WHERE adm = '5685') as balance