如何在SQL Server中使用别名添加两列？

您可以在outer query不alias生成相同查询的情况下执行此操作.

SELECT items_no, 
       item_desc, 
       item_qty, 
       grn_qty, 
       issues_qty, 
       total_qty = grn_qty + issues_qty 
FROM   (SELECT s.items_no, 
               s.item_desc, 
               s.item_qty, 
               (SELECT Isnull(Sum(g.qty), 0) 
                FROM   grn_details g 
                WHERE  g.items_no = s.items_no) grn_qty, 
               (SELECT Isnull(Sum(i.qty), 0) 
                FROM   stk_issue_details i 
                WHERE  i.items_no = s.items_no) issues_qty 
        FROM   stocks s) a 

或者你可以使用OUTER APPLY只select需要单身的地方

SELECT s.items_no, 
       s.item_desc, 
       s.item_qty, 
       grn_qty, 
       issues_qty, 
       total_qty = grn_qty + issues_qty 
FROM   stocks s 
       OUTER apply (SELECT Isnull(Sum(g.qty), 0) 
                    FROM   grn_details g 
                    WHERE  g.items_no = s.items_no) g(grn_qty) 
       OUTER apply (SELECT Isnull(Sum(i.qty), 0) 
                    FROM   stk_issue_details i 
                    WHERE  i.items_no = s.items_no) i (issues_qty)