postgresql如何显示每天日期的最频繁值
我对一个应该返回每个日期最多出现的值的查询有一个问题postgresql如何显示每天日期的最频繁值,sql,postgresql,Sql,Postgresql,我对一个应该返回每个日期最多出现的值的查询有一个问题 +------------+------------------+ | Date | value | +------------+------------------+ | 2020-01-01 | Programmer | | 2020-01-02 | Technician | | 2020-01-03 | Business Analyst | +------------+-----
+------------+------------------+
| Date | value |
+------------+------------------+
| 2020-01-01 | Programmer |
| 2020-01-02 | Technician |
| 2020-01-03 | Business Analyst |
+------------+------------------+
到目前为止,我已经做到了
select count(headline) as asd, publication_date, employer -> 'name' as dsa from jobhunter
group by publication_date,dsa
ORDER BY publication_date DESC
但它显示的是2020-12-31 19:06:00,而不仅仅是YYYY-MM-DD
你知道怎么解决这个问题吗?
测试数据:
create table tbl (
id serial primary key,
row_datetime TIMESTAMP,
row_val VARCHAR(60)
);
insert into tbl (row_datetime, row_val) values ('2021-01-01 00:00:00', 'a');
insert into tbl (row_datetime, row_val) values ('2021-01-01 01:00:00', 'a');
insert into tbl (row_datetime, row_val) values ('2021-01-01 02:00:00', 'b');
insert into tbl (row_datetime, row_val) values ('2021-01-02 00:00:00', 'a');
insert into tbl (row_datetime, row_val) values ('2021-01-02 01:00:00', 'b');
insert into tbl (row_datetime, row_val) values ('2021-01-02 02:00:00', 'b');
查询示例:
SELECT dt, val, cnt
FROM (
SELECT dt, val, cnt, ROW_NUMBER() OVER (PARTITION BY dt ORDER BY cnt DESC) AS row_num
FROM (
SELECT dt, val, COUNT(val) AS cnt
FROM (
SELECT DATE(row_datetime) AS dt, row_val AS val FROM tbl
) AS T1 GROUP BY dt, val
) AS T2
) AS T3
WHERE row_num=1
ORDER BY dt ASC
您还可以自定义查询以优化性能、获取更多字段等。太棒了,完全符合我的要求!