sql - Oracle查询时间范围

Question

下面是我自己的练习:

我创建了一个包含一些值的表，如:

CREATE TABLE my_test AS
SELECT ROWNUM ID, TRUNC(SYSDATE)+(LEVEL*5/24/60/60)date_time , 111 person_id
FROM dual CONNECT BY LEVEL <= (24*60*60)/5 
ORDER BY 1;

现在，我更新了表格，person_id = 222对于 date_time在 5:30 am 之间和 6:30 am

UPDATE my_test
SET  person_id   = 222
WHERE date_time >= trunc(SYSDATE)+ 5/24 + 30/24/60
 AND DATE_TIME  <= trunc(sysdate)+ 6/24 + 30/24/60;

我需要统计每个小时的人数，所以我写了这样的代码:

SELECT time_range,count(distinct person_id) PERSON_COUNT
FROM (
select person_id , date_time,
case TO_CHAR(date_time,'hh24') when '00' then '12 AM - 01 AM' 
             when '01' then '01 AM - 02 AM'
             when '02' then '02 AM - 03 AM'
             when '03' then '03 AM - 04 AM'
             when '04' then '04 AM - 05 AM'
             when '05' then '05 AM - 06 AM'
             when '06' then '06 AM - 07 AM'
             when '07' then '07 AM - 08 AM'
             when '08' then '08 AM - 09 AM'
             when '09' then '09 AM - 10 AM'
             when '10' then '10 AM - 11 AM'
             when '11' then '11 AM - 12 PM'
             when '12' then '12 PM - 01 PM'
             when '13' then '01 PM - 02 PM'
             when '14' then '02 PM - 03 PM'
             when '15' then '03 PM - 04 PM'
             when '16' then '04 PM - 05 PM'
             when '17' then '05 PM - 06 PM'
             when '18' then '06 PM - 07 PM'
             when '19' then '07 PM - 08 PM'
             when '20' then '08 PM - 09 PM'
             when '21' then '09 PM - 10 PM'
             when '22' then '10 PM - 11 PM'
             WHEN '23' THEN '11 PM - 12 AM' end time_range
FROM my_test
WHERE date_time >= trunc(SYSDATE)
AND date_time < trunc(SYSDATE)+1
ORDER BY date_time)
GROUP BY time_range;

它在没有预期顺序的情况下工作正常。 (time_range 的顺序没有给出预期的结果，因为它是外部查询中的字符串)。

我需要按 time_range 进行排序，感谢任何简单易用的上述代码。提前致谢。

Answer 1

ORDER BY 子句在单个查询中始终是最后解释的，但是这里它在子查询中，因此主查询 GROUP BY 将“覆盖”您的 ORDER BY。

你可以这样写:

SELECT time_range, COUNT(DISTINCT person_id) PERSON_COUNT
  FROM (SELECT person_id,
               date_time,
               CASE TO_CHAR(date_time, 'hh24')
                  WHEN '00' THEN
                   '12 AM - 01 AM'
               /*[snip]*/
                  WHEN '23' THEN
                   '11 PM - 12 AM'
               END time_range
          FROM my_test
         WHERE date_time >= trunc(SYSDATE)
           AND date_time < trunc(SYSDATE) + 1)
 GROUP BY time_range, TO_CHAR(date_time, 'hh24')
 ORDER BY TO_CHAR(date_time, 'hh24');

此外，我不喜欢您的 time_range 表达式。您可以简单地将其重写为:

to_char(date_time, 'HH PM - ') || to_char(date_time + 1/24, 'HH PM') time_range

编辑:显然你需要完整的查询:

SELECT time_range, COUNT(DISTINCT person_id) PERSON_COUNT
  FROM (SELECT person_id,
               date_time,
               to_char(date_time, 'HH PM - ') 
               || to_char(date_time + 1/24, 'HH PM')  time_range
          FROM my_test
         WHERE date_time >= trunc(SYSDATE)
           AND date_time < trunc(SYSDATE) + 1)
 GROUP BY time_range, TO_CHAR(date_time, 'hh24')
 ORDER BY TO_CHAR(date_time, 'hh24');