我无法使此查询与 SUM 函数一起使用答案

【问题标题】：I can't make this query work with SUM function我无法使此查询与 SUM 函数一起使用
【发布时间】：2011-02-10 12:03:35
【问题描述】：

此查询给出错误：

select ep, 
  case
    when ob is null and b2b_ob is null then 'a'
    when ob is not null or b2b_ob is not null then 'b'
    else null
  end as type,
  sum(b2b_d + b2b_t - b2b_i) as sales
from table
where ...
group by ep, type

错误：ORA-00904：“TYPE”：无效标识符

当我使用group by ep 运行它时，错误消息变为：

ORA-00979: 不是 GROUP BY 表达式

如果我删除sum(b2b_d+b2b_t-b2b_i) as sales 和group by ... 行，整个查询工作正常，所以问题应该与SUM 和GROUP BY 函数有关。我怎样才能使这项工作？提前感谢您的帮助。

【问题讨论】：

标签： sql oracle ora-00904 ora-00979

【解决方案1】：

不幸的是，SQL 不允许您在 GROUP BY 子句中使用列别名，因此您要么必须像这样重复整个 CASE：

select ep, 
  case
    when ob is null and b2b_ob is null then 'a'
    when ob is not null or b2b_ob is not null then 'b'
    else null
  end as type,
  sum(b2b_d + b2b_t - b2b_i) as sales
from table
where ...
group by ep,
  case
    when ob is null and b2b_ob is null then 'a'
    when ob is not null or b2b_ob is not null then 'b'
    else null
  end

或使用这样的内嵌视图：

select ep, 
  type,
  sum(b2b_d + b2b_t - b2b_i) as sales
from
( select ep, 
    case
      when ob is null and b2b_ob is null then 'a'
      when ob is not null or b2b_ob is not null then 'b'
      else null
    end as type,
    b2b_d,
    b2b_t,
    b2b_i
  from table
  where ...
)
group by ep, type

【讨论】：