Question

select room_id,count (distinct(patient_id)) as patient_id 
from patient_flow where time='CURRENT_TIME';

我需要当前时间相应room_ids的患者ID数量。

 id | patient_id  | room_id |        time
----+-------------+---------+---------------------
  1 | 00035-67351 |       1 | 2015-06-09 10:11:20
  1 | 00035-67351 |       2 | 2015-06-09 10:31:20
  1 | 00035-67351 |       1 | 2015-06-09 10:12:20
  1 | 00035-67351 |       1 | 2015-06-09 10:12:40
  1 | 00035-67351 |       1 | 2015-06-09 10:15:40
  1 | 00035-67351 |       1 | 2015-06-09 10:30:40
  1 | 00035-67351 |       2 | 2015-06-09 10:32:40
  1 | 00035-67351 |       2 | 2015-06-09 10:36:40
  1 | 00035-67351 |       2 | 2015-06-09 10:38:40
  1 | 00035-67351 |       2 | 2015-06-09 10:50:40

我写了上面的查询，但它没有执行。

Answer 1

使用汇总功能GROUP BY时，您错过了COUNT()。以下查询将起作用：

SELECT room_id, COUNT (DISTINCT(patient_id)) AS patient_id 
FROM patient_flow 
WHERE time = CURRENT_DATE
GROUP BY room_id;

Answer 2

select current_time, room_id, count (distinct(patient_id)) as patient_id from patient_flow  group by room_id;

我在执行上述查询时得到了结果..

查询PSQL确定系统当前时间内的患者数量

2 个答案: