How to select data from day by day with special time? - sql

Question

I want to select data day by day. Condition: data will be cut the day from 10:00 pm to tomorrow 10 pm. For example:
| REGTIME | T8 | T9 | T10 |
| 2008-12-03 | 879 | 785| 542 |
| 2008-12-04 | 556 | 454| 321 |
| 2008-12-05 | 678 | 122| 212 |
| 2008-12-06 | 887 | 544| 214 |
(2008-12-03 data will be show from 2008-12-02 10:00pm to 2008-12-03 10:00 pm)...
That query shows me all date, but it shows day with all same value.
SELECT REGTIME2,
A.T8,T9,T10
FROM
( SELECT
SUM(CASE WHEN sdudent_type = 'AAAA1' THEN 1 ELSE 0 END) AS T8,
SUM(CASE WHEN sdudent_type = 'AAAA2' THEN 1 ELSE 0 END) AS T9,
SUM(CASE WHEN sdudent_type = 'AAAA3' THEN 1 ELSE 0 END) AS T10
FROM class_men C
WHERE REGTIME >= TO_DATE(:REGTIME_from,'YYYYMMDDHH24MISS')
AND REGTIME < TO_DATE(:REGTIME_to,'YYYYMMDDHH24MISS')
) A,
(
select distinct
to_char(REGTIME,'YYYY-MM-DD') AS REGTIME2
from class_men
group by REGTIME
order by to_char(REGTIME,'YYYY-MM-DD') desc
) B

Answer 1

You are getting the results duplicated for all days as you are using a CROSS JOIN (written in the legacy syntax using a comma) to join the two SELECT clauses and there is no correlation between those two statements.
You appear to want something like:
SELECT TRUNC( RegTime ) AS RegTime,
COUNT(CASE WHEN sdudent_type = 'AAAA1' THEN 1 END) AS T8,
COUNT(CASE WHEN sdudent_type = 'AAAA2' THEN 1 END) AS T9,
COUNT(CASE WHEN sdudent_type = 'AAAA3' THEN 1 END) AS T10
FROM class_men C
WHERE REGTIME >= TO_DATE(:REGTIME_from,'YYYYMMDDHH24MISS')
AND REGTIME < TO_DATE(:REGTIME_to,'YYYYMMDDHH24MISS')
GROUP BY TRUNC( RegTime );
or using TO_CHAR( RegTime, 'YYYY-MM-DD' ) instead of TRUNC( RegTime ).
Which, for the sample data:
CREATE TABLE class_men ( regTime, sdudent_type ) AS
SELECT DATE '2021-01-01' + INTERVAL '1' MINUTE * LEVEL, 'AAAA1'
FROM DUAL CONNECT BY LEVEL <= 250 UNION ALL
SELECT DATE '2021-01-01' + INTERVAL '1' MINUTE * LEVEL, 'AAAA2'
FROM DUAL CONNECT BY LEVEL <= 42 UNION ALL
SELECT DATE '2021-01-01' + INTERVAL '1' MINUTE * LEVEL, 'AAAA3'
FROM DUAL CONNECT BY LEVEL <= 13 UNION ALL
SELECT DATE '2021-01-02' + INTERVAL '1' MINUTE * LEVEL, 'AAAA1'
FROM DUAL CONNECT BY LEVEL <= 99 UNION ALL
SELECT DATE '2021-01-02' + INTERVAL '1' MINUTE * LEVEL, 'AAAA2'
FROM DUAL CONNECT BY LEVEL <= 17 UNION ALL
SELECT DATE '2021-01-02' + INTERVAL '1' MINUTE * LEVEL, 'AAAA3'
FROM DUAL CONNECT BY LEVEL <= 24 UNION ALL
SELECT DATE '2021-01-03' + INTERVAL '1' MINUTE * LEVEL, 'AAAA1'
FROM DUAL CONNECT BY LEVEL <= 23 UNION ALL
SELECT DATE '2021-01-03' + INTERVAL '1' MINUTE * LEVEL, 'AAAA3'
FROM DUAL CONNECT BY LEVEL <= 50;
Would output (for the range 20210101000000 to 20210104000000):
REGTIME | T8 | T9 | T10
:------------------ | --: | -: | --:
2021-01-01 00:00:00 | 250 | 42 | 13
2021-01-03 00:00:00 | 23 | 0 | 50
2021-01-02 00:00:00 | 99 | 17 | 24
(Note: the date format depends on the NLS_DATE_FORMAT session parameter [unless you use TO_CHAR].)
db<>fiddle here