如何使用4gl中的变量“分组”

是的，当然你可以，非常基本的：

    
      DEFINE VARIABLE v-sell-price AS INTEGER NO-UNDO.
DEFINE VARIABLE v-cost-price AS INTEGER NO-UNDO.
FOR EACH order BREAK BY order.invoice:
/* Sum the prices */
ASSIGN 
    v-sell-price = v-sell-price + Order.sell-price.
    v-cost-price = v-cost-price + Order.cost-price. 
/* On the last order matching this order display and reset sums */
IF LAST-OF(order.invoice) THEN DO:
    DISPLAY Order.invoice v-sell-price v-cost-price.
    ASSIGN 
        v-sell-price = 0
        v-cost-price = 0.
END.
END.
</code>
  

实际上这就是ACCUMULATE STATEMENT和ACCUM功能的用途。
我找到了那些有点难以记住的确切语法（有时甚至在阅读了在线帮助后很难理解），所以我常常像Jensd的答案​​那样自己积累变量。
您的示例的代码应如下所示（语法已检查但未经过测试）：

    
      FOR EACH order BREAK BY order.invoice:
accumulate Order.sell-price (sub-total by order.invoice).
accumulate Order.cost-price (sub-total by order.invoice).
IF LAST-OF(order.invoice) THEN
    DISPLAY Order.invoice 
      accum sub-total by order.invoice Order.sell-price
      accum sub-total by order.invoice Order.cost-price.
END.
</code>