sql减去子查询总和多个表

Question

如何从另一个表中减去子查询表的总和？

SELECT i.column1 * i.column2 AS Expr1 
    , i.column1 * i.column2 - (SELECT SUM(table2.column1) AS Expr1 
           FROM table2 
           WHERE (table2.column3 = table1.column3)) AS derivedExpression 
FROM table1 

只有第一行中的derivedExpression是正确的。其余行为derivedExpression返回null。对于Expr1，一切都很好。任何帮助？

Answer 1

SELECT i.column1 * i.column2 AS Expr1 
    , i.column1 * i.column2 - (SELECT COALESCE(SUM(table2.column1), 0) AS Expr1 
           FROM table2 
           WHERE (table2.column3 = table1.column3)) AS derivedExpression 
FROM table1