从两个表中减去派生列

Question

我有两个表格，sept和费用，我需要从费用中选择已支付的总额，并从seet的应付金额中减去。

我用以下查询尝试过它，有人可以纠正它吗？

我收到此错误：

每个派生表必须具有自己的别名

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