相关子查询 SQL Server 2014

Question

我（未成功）在 Invoices 表上使用相关子查询：

Invoices(InvoiceID,  VendorID, InvoiceTotal, PaymentTotal, CreditTotal,.... ),

找到所有供应商的最大未付发票的总和，其中未付条件由下式给出InvoiceTotal-PaymentTotal-CreditTotal <0：

 Select Sum(LargestUnpaid) from 
 (Select   Max(InvoiceTotal) AS LargestUnpaid from Invoices 
  where InvoiceTotal-(PaymentTotal+CreditTotal)<0 group by vendorID ) ;

内部查询运行，有好有坏，因为查询应该是相关的，但查询作为一个整体没有运行，我收到错误消息：

Msg 102, Level 15, State 1, Line 4 Incorrect syntax near ')'.

我究竟做错了什么？

Answer 1

在;例如VendLargestUnpaidInv之前为派生表添加别名：

Select Sum(LargestUnpaid) from
 (Select   Max(InvoiceTotal) AS LargestUnpaid from Invoices 
  where InvoiceTotal-(PaymentTotal+CreditTotal)<0 group by vendorID ) VendLargestUnpaidInv;