SQL CASE WHEN：是否有限制（字符数）？ [关闭]答案

【问题标题】：SQL CASE WHEN: is there a limit ( in number of characters )? [closed]SQL CASE WHEN：是否有限制（字符数）？ [关闭]
【发布时间】：2021-10-12 08:19:43
【问题描述】：

我正在使用 case when 语句将位置（起点和终点纬度、经度）分组为 3 个区域。

为每个区域运行 1 个查询工作正常。

只需将所有区域捆绑在一个查询中，结果为空。

select    period
        , case 
          when ( in_polygon("polygon", starting_lng, starting_lat, <coordinates_1__5739_characters> ) = True
            or   in_polygon("polygon",     dest_lng,     dest_lat, <coordinates_1__5739_characters> ) = True )
          then 'Region 1'
          end as region
        , sum(<metrics>)
from source_table
where <conditions>
group by period, starting_lng, starting_lat, dest_lng, dest_lat

select    period
        , case 
          when ( in_polygon("polygon", starting_lng, starting_lat, <coordinates_2__2471_characters> ) = True
            or   in_polygon("polygon",     dest_lng,     dest_lat, <coordinates_2__2471_characters> ) = True ) 
          then 'Region 2'
          end as region
        , sum(<metrics>)
from source_table
where <conditions>
group by period, starting_lng, starting_lat, dest_lng, dest_lat

select    period
        , case 
          when ( in_polygon("polygon", starting_lng, starting_lat, <coordinates_3__3039_characters> ) = True
            or   in_polygon("polygon",     dest_lng,     dest_lat, <coordinates_3__3039_characters> ) = True )
          then 'Region 3'
          end as region
        , sum(<metrics>)
from source_table
where <conditions>
group by period, starting_lng, starting_lat, dest_lng, dest_lat

上面的 3 个查询工作正常。以下一项结果为空：

select    period
        , case 
          when ( in_polygon("polygon", starting_lng, starting_lat, <coordinates_1__5739_characters> ) = True
            or   in_polygon("polygon",     dest_lng,     dest_lat, <coordinates_1__5739_characters> ) = True )
          then 'Region 1'
          when ( in_polygon("polygon", starting_lng, starting_lat, <coordinates_2__2471_characters> ) = True
            or   in_polygon("polygon",     dest_lng,     dest_lat, <coordinates_2__2471_characters> ) = True ) 
          then 'Region 2' 
          when ( in_polygon("polygon", starting_lng, starting_lat, <coordinates_3__3079_characters> ) = True
            or   in_polygon("polygon",     dest_lng,     dest_lat, <coordinates_3__3079_characters> ) = True )
          then 'Region 3'
          end as region
        , sum(<metrics>)
from source_table
where <conditions>
group by period, starting_lng, starting_lat, dest_lng, dest_lat

观察到坐标字符串很长，这促使我尝试分离区域。

(2 x 5,739 + 2 x 2,417 + 2 x 3,079) = 22,578

我希望你的想法是：

case when 语句有限制吗？如果是，上限是多少个字符？
有什么比将查询分成三个更实用的解决方案？

【问题讨论】：

标记您正在使用的 DBMS。顺便说一句，你拥有的是CASE 表达式，而不是语句。

标签： sql case limit presto

【解决方案1】：

这应该可行：

select    period
        , case 
          when ( in_polygon("polygon", starting_lng, starting_lat, <coordinates_1__5739_characters> ) = True
            or   in_polygon("polygon",     dest_lng,     dest_lat, <coordinates_1__5739_characters> ) = True )
          then 'True' else 'False' end as region1,
          case  when ( in_polygon("polygon", starting_lng, starting_lat, <coordinates_2__2471_characters> ) = True
            or   in_polygon("polygon",     dest_lng,     dest_lat, <coordinates_2__2471_characters> ) = True ) 
          then 'True' else 'False' end as region2, 
          case  when ( in_polygon("polygon", starting_lng, starting_lat, <coordinates_3__3079_characters> ) = True
            or   in_polygon("polygon",     dest_lng,     dest_lat, <coordinates_3__3079_characters> ) = True )
          then 'True' else 'False' end as region3,    
        , sum(<metrics>)
from source_table
where <conditions>
group by period, starting_lng, starting_lat, dest_lng, dest_lat

【讨论】：

非常感谢，院长！它有效