如何合并DISTINCT和计算合计值

Question

I have a table with subjects with the columns capture_group_id, subject_id, and round_id and some other columns. I want to write a SELECT statement which returns the distinct subjects without paying regard to the round_id, but i want also to know in how many rounds the Subject participated.

I've come to these two Solutions (which aren't returning the result in the needed form)

FIRST:

SELECT study_case.capture_group_id, proband.subject_id,Count(1) AS Count
FROM study_case
JOIN proband
ON study_case.proband_id = proband.proband_id
GROUP BY study_case.capture_group_id, proband.subject_id

this returns the distinct subjects with the count of participated rounds. But i can't add columns to the select statement whicht aren't included in the group by statement.

Another approach was:

SELECT DISTINCT ON (study_case.capture_group_id, proband.subject_id) study_case.capture_group_id, proband.subject_id, study_case.round_id, proband.gender, proband.birth_year, proband.birth_country

FROM study_case
JOIN proband
ON study_case.proband_id = proband.proband_id
ORDER BY study_case.capture_group_id, proband.subject_id, study_case.round_id

How can I build a SQL Statment which shows the distinct subjects, counts the DISTINCT aggregated Subjects and includes all columns from the second statement?

Answer 1

You can do what you want with window functions:

SELECT capture_group_id, subject_id, round_id, gender, birth_year, birth_country, cnt
FROM (SELECT sc.capture_group_id, p.subject_id, sc.round_id, p.gender,
             p.birth_year, p.birth_country,
             row_number() over (partition by study_case.capture_group_id, p.subject_id
                                order by sc.capture_group_id, p.subject_id, sc.round_id
                               ) as seqnum,
             count(*) over (partition by sc.capture_group_id, p.subject_id) as cnt
      FROM study_case sc JOIN
           proband p
           ON sc.proband_id = p.proband_id
     ) t
WHERE seqnum = 1
ORDER BY capture_group_id, subject_id, round_id