如何在 HANA 中进行案例

Question

我在 postgres 中有以下查询，它给出了仪表范围以及该范围内行驶的车辆数量

SELECT (CASE WHEN meter >= 0 AND meter< 10000 THEN '0-10' 
             WHEN meter >= 10000 AND meter < 20000  THEN '10-20' 
             WHEN meter >= 20000 AND meter <30000 THEN '20-30' 
             WHEN meter >= 30000 AND meter < 40000 THEN '30-40' 
             WHEN meter >= 40000 AND meter < 50000 THEN '40-50' 
             WHEN meter >= 50000 AND meter < 60000  THEN '50-60' 
             WHEN meter >= 60000 AND meter <70000 THEN '60-70' 
             WHEN meter >= 70000 AND meter < 80000 THEN '70-80' 
             WHEN meter >= 80000 AND meter < 100000 THEN '80-90' 
             WHEN meter >=100000 THEN 'above 100'  
       END) as range,count(*) as vehicle_count 
        from ( 



      SELECT extract (day from time) as day, place,vehicle_id,sum(meter_two_points) as meter 
FROM public.datatable where time >= '2015-09-05 00:00:00' and time <= '2015-09-05 23:00:00' and place=10 
  group by day,vehicle_id,place 
  order by day,vehicle_id  



)  as A group by range  order by range limit 10

我现在想对 HANA 中的同一个表执行相同的查询。所以我尝试使用

 SELECT (CASE   WHEN meter >= 0 AND meter< 10000 THEN '0-10' 
                WHEN meter >= 10000 AND meter < 20000  THEN '10-20' 
                WHEN meter >= 20000 AND meter <30000 THEN '20-30' 
                WHEN meter >= 30000 AND meter < 40000 THEN '30-40' 
                WHEN meter >= 40000 AND meter < 50000 THEN '40-50' 
                WHEN meter >= 50000 AND meter < 60000  THEN '50-60' 
                WHEN meter >= 60000 AND meter <70000 THEN '60-70' 
                WHEN meter >= 70000 AND meter < 80000 THEN '70-80' 
                WHEN meter >= 80000 AND meter < 100000 THEN '80-90' 
                WHEN meter >=100000 THEN 'above 100'  
           END) as range,count(*) as vehicle_count 
            from ( 


            But it throws with the error `invalid column name range`
          SELECT to_integer(to_varchar(time,'DD')) as day, place,vehicle_id,sum(meter_two_points) as meter 
    FROM public.datatable where time >= '2015-09-05 00:00:00' and time <= '2015-09-05 23:00:00' and place=10 
      group by day,vehicle_id,place 
      order by day,vehicle_id  



    )  as A group by range  order by range limit 10

Answer 1

您可以更改为：

SELECT range, 
    COUNT(*) AS vehicle_count 
FROM (
    SELECT (CASE   WHEN meter >= 0 AND meter< 10000 THEN '0-10' 
                WHEN meter >= 10000 AND meter < 20000  THEN '10-20' 
                WHEN meter >= 20000 AND meter <30000 THEN '20-30' 
                WHEN meter >= 30000 AND meter < 40000 THEN '30-40' 
                WHEN meter >= 40000 AND meter < 50000 THEN '40-50' 
                WHEN meter >= 50000 AND meter < 60000  THEN '50-60' 
                WHEN meter >= 60000 AND meter <70000 THEN '60-70' 
                WHEN meter >= 70000 AND meter < 80000 THEN '70-80' 
                WHEN meter >= 80000 AND meter < 100000 THEN '80-90' 
                WHEN meter >=100000 THEN 'above 100'  
           END) AS range
    FROM ( 
        SELECT to_integer(to_varchar(time,'DDMMYYYY')) AS day, 
            --You should considering using other way to truncate date from time, 
            --not convert too much,
            --at least you could use only to_varchar is enough
            place, 
            vehicle_id,
            SUM(meter_two_points) AS meter 
        FROM public.datatable 
        WHERE time >= '2015-09-05 00:00:00' 
            AND time <= '2015-09-05 23:00:00' 
            AND place=10 
        GROUP BY to_integer(to_varchar(time,'DDMMYYYY')), 
            vehicle_id, 
            place 
    )  
) AS a
GROUP BY range  
ORDER BY range 
LIMIT 10;       --why limit 10 here while you only have 10 ranges?

并且作为 SQL 操作顺序，我一直想知道 PostgreSQL 是否可以

GROUP BY

在

SELECT

之后，所以 group by 可以在第一个查询中与范围列进行分组。

Answer 2

这里是 SELECT 语句中 CASE 的示例，取自文章 “Declaraciones CASE en Consultas OPEN SQL usando ABAP 7.4”，ABAP.ar：