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[英]How to select one unique value in mysql for the first row then show nothing for that value, BUT show all the records?
[英]How to SELECT two records for each unique column value as one row in MySQL?
我有一个像这样的 MySQL 表:
+----+-----+-------+------+------+-------+---------------------+
| ID | GID | Name | p1 | p10 | p100 | createdAt |
+----+-----+-------+------+------+-------+---------------------+
| 1 | 100 | Item1 | 150 | 1499 | 10245 | 2020-07-04 12:00:00 |
| 2 | 857 | Item2 | 1047 | 9875 | 90000 | 2020-07-04 12:00:10 |
| 3 | 100 | Item1 | 149 | 1495 | 10245 | 2020-07-04 12:15:00 |
| 4 | 857 | Item2 | 1099 | 9875 | 89999 | 2020-07-04 12:15:10 |
| 5 | 100 | Item1 | 149 | 1495 | 10247 | 2020-07-04 12:30:00 |
| 6 | 857 | Item2 | 970 | 9879 | 89998 | 2020-07-04 12:30:10 |
+----+-----+-------+------+------+-------+---------------------+
我尝试的是createdAt
为每个唯一的GID
值他们最近创建的两个p1, p10, p100
Output 示例:
+-----+-------+------+------+-------+---------+----------+-----------+
| GID | Name | p1 | p10 | p100 | p1-last | p10-last | p100-last |
+-----+-------+------+------+-------+---------+----------+-----------+
| 100 | Item1 | 149 | 1495 | 10245 | 149 | 1495 | 10247 |
| 857 | Item2 | 1099 | 9875 | 89999 | 970 | 9879 | 89998 |
+-----+-------+------+------+-------+---------+----------+-----------+
我试图使用子查询来实现我的目标,但我对此并不满意。
感谢任何可以为我提供信息和帮助的人。
您将为此使用lag()
:
select gid, name, p1, p10, p100, prev_p1, prev_p10, prev_p100
from (select t.*,
lag(p1) over (partition by gid order by createdAt) as prev_p1,
lag(p10) over (partition by gid order by createdAt) as prev_p10,
lag(p100) over (partition by gid order by createdAt) as prev_p100,
row_number() over (partition by gid order by createdAt desc) as seqnum
from t
) t
where seqnum = 1;
这是一个 db<>fiddle。
子查询返回每列的先前值。 外部查询只是过滤到每个gid
/ name
组合的最新行。
没有 window 函数,这并不容易和优雅。
这是一种方法,它涉及自连接、2 级聚合和条件聚合:
select t.gid, t.name,
max(case when c.counter = 1 then t.p1 end) p1,
max(case when c.counter = 1 then t.p10 end) p10,
max(case when c.counter = 1 then t.p100 end) p100,
max(case when c.counter = 0 then t.p1 end) p1_last,
max(case when c.counter = 0 then t.p10 end) p10_last,
max(case when c.counter = 0 then t.p100 end) p100_last
from tablename t inner join (
select t1.gid, t1.createdat, count(t2.createdat) counter
from tablename t1 left join tablename t2
on t2.gid = t1.gid and t1.createdat < t2.createdat
group by t1.gid, t1.createdat
having count(t2.createdat) <= 1
) c on c.gid = t.gid and c.createdat = t.createdat
group by t.gid, t.name
见演示。
结果:
| gid | name | p1 | p10 | p100 | p1_last | p10_last | p100_last |
| --- | ----- | ---- | ---- | ----- | ------- | -------- | --------- |
| 100 | Item1 | 149 | 1495 | 10245 | 149 | 1495 | 10247 |
| 857 | Item2 | 1099 | 9875 | 89999 | 970 | 9879 | 89998 |
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