Question

我正在查询下面运行

Select location, sum(units) as Units
from
( Select a.from_loc as location, sum(units) as units
from emp a, dept b
where a.id=b.id
Union all
Select a.to_loc as location, sum(units) as units
feom emp a, dept b
where a.id=b.id)
group by location;

以上查询以以下格式提供了我的数据。

Location | sum(Units)
--------------------
100      |  350
200      |  450

现在我需要用上述查询给定的单位更新另一个表类。班级将“位置”作为主键列，并将“单位”列也包含在内。

我试图创建一个游标，但是它抛出错误，因为无法使用更新

这是光标代码的片段

Declare
V_location number(20);
V_units (20),
Cursor c1 is
Select location, sum(units) as Units
from
 ( Select a.from_loc as location, sum(units) as units
   from emp a, dept b
    where a.id=b.id
    Union all
    Select a.to_loc as location, sum(units) as units
     from emp a, dept b
     where a.id=b.id)
      group by location -----above select query
 for update;
Begin
 Open c1;
 Loop
 Fetch c1 into v_location, v_units;
 Exit when c1%notfound;

 Update class set units=v_units
 where location=v_location;
  End loop;
  Close c1;
 End;

它的抛出不允许更新此查询表达式有人可以让我知道我在这里做错了什么。或其他一些方法来更新类表

Answer 1

这有好处吗？

我认为FOR UPDATE子句会引起问题
我删除了整个DECLARE部分，并在游标SELECT循环中使用了FOR语句，因为它易于维护（无打开，关闭，退出等）。 / li>

BEGIN
   FOR cur_r IN (  SELECT location, SUM (units) AS units
                     FROM (SELECT a.from_loc AS location, SUM (units) AS units
                             FROM emp a, dept b
                            WHERE a.id = b.id
                           UNION ALL
                           SELECT a.to_loc AS location, SUM (units) AS units
                             FROM emp a, dept b
                            WHERE a.id = b.id)
                 GROUP BY location)
   LOOP
      UPDATE class
         SET units = cur_r.units
       WHERE location = cur_r.location;
   END LOOP;
END;

[阅读评论后，编辑]

IF-THEN-ELSE将使用CASE（或DECODE）来完成；例如：

update class set
  units = case when location between 1 and 100 then cur_r.units / 10
               else cur_r.units / 20
          end
where location = cur_r.location

不允许更新此查询表达式（游标）

1 个答案: