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[英]How to select if `col1 = 0 OR col2 = 0 OR col3 != null` statement in postgresql?
[英]How can I get the sum(value) on the latest gather_time per group(name,col1) in PostgreSQL?
實際上,我對下面的線程中的類似問題得到了一個很好的答案,但我還需要一個針對不同數據集的解決方案。
數據集包含歷史數據,我只想在最新的gather_time上獲取該組的總和(值)。 最終結果應如下:
name | col1 | gather_time | sum
-------+------+---------------------+-----
first | 100 | 2016-01-01 23:12:49 | 6
first | 200 | 2016-01-01 23:11:13 | 4
但是,我只能看到一組(前100個)的數據,下面的查詢意味着第二組沒有數據(第一個200)。 事情是我需要每組獲得一行。 該組的數量可以變化。
select name,col1,gather_time,sum(value)
from testtable
group by name,col1,gather_time
order by gather_time desc
limit 2;
name | col1 | gather_time | sum
-------+------+---------------------+-----
first | 100 | 2016-01-01 23:12:49 | 6
first | 100 | 2016-01-01 23:11:19 | 6
(2 rows)
你能建議我完成這個要求嗎?
create table testtable
(
name varchar(30),
col1 varchar(30),
col2 varchar(30),
gather_time timestamp,
value integer
);
insert into testtable values('first','100','q1','2016-01-01 23:11:19',2);
insert into testtable values('first','100','q2','2016-01-01 23:11:19',2);
insert into testtable values('first','100','q3','2016-01-01 23:11:19',2);
insert into testtable values('first','200','t1','2016-01-01 23:11:13',2);
insert into testtable values('first','200','t2','2016-01-01 23:11:13',2);
insert into testtable values('first','100','q1','2016-01-01 23:11:11',2);
insert into testtable values('first','100','q1','2016-01-01 23:12:49',2);
insert into testtable values('first','100','q2','2016-01-01 23:12:49',2);
insert into testtable values('first','100','q3','2016-01-01 23:12:49',2);
select *
from testtable
order by name,col1,gather_time;
name | col1 | col2 | gather_time | value
-------+------+------+---------------------+-------
first | 100 | q1 | 2016-01-01 23:11:11 | 2
first | 100 | q2 | 2016-01-01 23:11:19 | 2
first | 100 | q3 | 2016-01-01 23:11:19 | 2
first | 100 | q1 | 2016-01-01 23:11:19 | 2
first | 100 | q3 | 2016-01-01 23:12:49 | 2
first | 100 | q1 | 2016-01-01 23:12:49 | 2
first | 100 | q2 | 2016-01-01 23:12:49 | 2
first | 200 | t2 | 2016-01-01 23:11:13 | 2
first | 200 | t1 | 2016-01-01 23:11:13 | 2
一種選擇是將原始表連接到一個表,該表僅包含每個name
col1
組的最新gather_time
記錄。 然后,您可以獲取每個組的value
列的總和,以獲得所需的結果集。
SELECT t1.name, t1.col1, MAX(t1.gather_time) AS gather_time, SUM(t1.value) AS sum
FROM testtable t1 INNER JOIN
(
SELECT name, col1, col2, MAX(gather_time) AS maxTime
FROM testtable
GROUP BY name, col1, col2
) t2
ON t1.name = t2.name AND t1.col1 = t2.col1 AND t1.col2 = t2.col2 AND
t1.gather_time = t2.maxTime
GROUP BY t1.name, t1.col1
如果您想在WHERE
子句中使用子查詢,就像在OP中嘗試的那樣,要僅限制使用最新gather_time
記錄,那么您可以嘗試以下操作:
SELECT name, col1, gather_time, SUM(value) AS sum
FROM testtable t1
WHERE gather_time =
(
SELECT MAX(gather_time)
FROM testtable t2
WHERE t1.name = t2.name AND t1.col1 = t2.col1
)
GROUP BY name, col1
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