SQL 查询未按预期给出结果
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【中文标题】SQL 查询未按预期给出结果【英文标题】:SQL query not giving result as expected 【发布时间】:2018-04-19 02:21:21 【问题描述】:我需要一些帮助。我有下表(示例如下所示):
EmpID | Type | timestamp | block_id
----------------------------------------------------
1 | 'R' | 2018-04-15 01:13:15 | AB12D
1 | 'P' | 2018-04-15 05:13:15
1 | 'P' | 2018-04-15 05:13:15
1 | 'P' | 2018-04-15 05:13:15
1 | 'D' | 2018-04-15 07:13:15
1 | 'D' | 2018-04-15 08:13:15
1 | 'D' | 2018-04-15 10:13:15
1 | 'R' | 2018-04-15 13:13:00 | 1X1#1
1 | 'P' | 2018-04-15 13:15:15
1 | 'P' | 2018-04-15 13:15:15
1 | 'P' | 2018-04-15 13:15:15
1 | 'D' | 2018-04-15 14:13:00
1 | 'D' | 2018-04-15 15:13:00
1 | 'D' | 2018-04-15 16:13:37
2 | 'R' | 2018-04-15 04:15:00 | __08XA
2 | 'P' | 2018-04-15 04:20:00
2 | 'D' | 2018-04-15 05:11:33
我正在尝试获得如下输出:
EmpID | begin_timestamp | end_timestamp | block_id | P_count | D_count
---------------------------------------------------------------------------------
1 | 2018-04-15 01:13:15 |2018-04-15 10:13:15 | AB12D | 3 | 3
1 | 2018-04-15 13:13:00 | 2018-04-15 16:13:37| 1X1#1 | 3 | 3
2 | 2018-04-15 04:15:00 | 2018-04-15 05:11:33| __08XA | 1 | 1
即,这些是某种块,每个 empId 可以有多个块。所以从上面的示例表中,empID '1' 有 2 个块(从第 1 行开始到第 7 行),第 2 个块从第 8 行到第 14 行; empID 2 有 1 个区块,第 14 行到第 16 行。
block_id
是一个字母数字字段,可以有任何随机值。此外,该表未按上述顺序排列,仅用于说明目的。我在红移,到目前为止有以下查询:
select CAST(timestamp AS DATE) as date, execution_id, min(timestamp) as begin_timestamp, max(timestamp) as end_timestamp, new_block_id,
sum(case when Type = 'P' then 1 else 0 end) as P_count,
sum(case when Type = 'D' then 1 else 0 end) as D_count
from (
select *,
max(block_id) over (partition by EmpID order by timestamp ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) new_block_id from myTable
) d
group by EmpID, new_block_id, CAST(timestamp AS DATE)
order by EmpID, new_block_id, CAST(timestamp AS DATE)
但这不起作用,因为它没有给出准确的结果。请帮忙!!
【问题讨论】:
【参考方案1】:你真正想要的是lag(ignore nulls)
,但 Postgres 不支持。
相反,您可以使用非 NULL 值的时间戳并使用它来定义组。
select date_trunc('day', timestamp) as date, execution_id,
min(timestamp) as begin_timestamp, max(timestamp) as end_timestamp,
max(block_id) as block_id,
sum(case when Type = 'P' then 1 else 0 end) as P_count,
sum(case when Type = 'D' then 1 else 0 end) as D_count
from (select t.*,
max(case when block_id is not null then timestamp end) over
(partition by EmpId
order by timestamp
rows between unbounded preceding and current row
) as grp
from myTable t
) t
group by empId, grp, date_trunc('day', timestamp)
【讨论】:
你是什么意思“你可以使用非NULL值的时间戳并用它来定义组”?如果有另一个 EmpID 具有相同的时间戳等怎么办? @Anjali 。 . .这没有什么区别。empId
是 partition by 和 group by 子句的一部分。
这里有没有办法实现 lag(ignore null) 作为解决方法?以上是关于SQL 查询未按预期给出结果的主要内容,如果未能解决你的问题,请参考以下文章