Sql Postgres:使用子查询更新表列
我有一个旅行GPS取样表:Sql Postgres:使用子查询更新表列,sql,postgresql,window-functions,Sql,Postgresql,Window Functions,我有一个旅行GPS取样表: SELECT * FROM trajecttories_splitted; user_id | session_id | timestamp | lat | lon | alt ---------+----------------+------------------------+-----------+------------+----- 1 | 20081023025304 | 2008-
SELECT * FROM trajecttories_splitted;
user_id | session_id | timestamp | lat | lon | alt
---------+----------------+------------------------+-----------+------------+-----
1 | 20081023025304 | 2008-10-23 02:53:04+01 | 39.984702 | 116.318417 | 492
1 | 20081023025304 | 2008-10-23 02:53:10+01 | 39.984683 | 116.31845 | 492
1 | 20081023025304 | 2008-10-23 02:53:15+01 | 39.984686 | 116.318417 | 492
1 | 20081023025304 | 2008-10-23 02:53:20+01 | 39.984688 | 116.318385 | 492
1 | 20081023025304 | 2008-10-23 02:53:25+01 | 39.984655 | 116.318263 | 492
1 | 20081023025304 | 2008-10-23 02:53:30+01 | 39.984611 | 116.318026 | 493
1 | 20081023025304 | 2008-10-23 02:53:35+01 | 39.984608 | 116.317761 | 493
1 | 20081023025304 | 2008-10-23 02:53:40+01 | 39.984563 | 116.317517 | 496
1 | 20081023025304 | 2008-10-23 02:53:45+01 | 39.984539 | 116.317294 | 500
1 | 20081023025304 | 2008-10-23 02:53:50+01 | 39.984606 | 116.317065 | 505
然后为了便于分析,我添加了一列采样率
,以跟踪连续行之间的GPS采样间隔
现在我想将新列的值设置为差异:种类row[sampling\u rate]=timestamp-LAG(timestamp)
因此,我使用:
UPDATE trajectories_splitted
SET sampling_rate=timestamp -LAG(timestamp) OVER (
PARTITION BY user_id
ORDER BY session_id
)
ERROR: window functions are not allowed in UPDATE
LINE 2: SET sampling_rate=timestamp -LAG(timestamp) OVER (
预期成果:
user_id | session_id | timestamp | lat | lon | alt | sampling_rate
---------+----------------+------------------------+-----------+------------+-----+---------------
1 | 20081023025304 | 2008-10-23 02:53:04+01 | 39.984702 | 116.318417 | 492 |
1 | 20081023025304 | 2008-10-23 02:53:10+01 | 39.984683 | 116.31845 | 492 | 6
1 | 20081023025304 | 2008-10-23 02:53:15+01 | 39.984686 | 116.318417 | 492 | 5
1 | 20081023025304 | 2008-10-23 02:53:20+01 | 39.984688 | 116.318385 | 492 | 10
1 | 20081023025304 | 2008-10-23 02:53:25+01 | 39.984655 | 116.318263 | 492 | 5
1 | 20081023025304 | 2008-10-23 02:53:30+01 | 39.984611 | 116.318026 | 493 | 5
1 | 20081023025304 | 2008-10-23 02:53:35+01 | 39.984608 | 116.317761 | 493 | 5
1 | 20081023025304 | 2008-10-23 02:53:40+01 | 39.984563 | 116.317517 | 496 | 5
1 | 20081023025304 | 2008-10-23 02:53:45+01 | 39.984539 | 116.317294 | 500 | 5
1 | 20081023025304 | 2008-10-23 02:53:50+01 | 39.984606 | 116.317065 | 505 | 5
编辑
根据下面的第一个答案,postgres
报告错误:
ERROR: column "sampling_rate" is of type timestamp with time zone but expression is of type interval
LINE 2: set sampling_rate = ts.timestamp - tts.prev_timestamp
如果可能有帮助,以下是表结构:
\d trajectories_splitted
Table "postgres.trajectories_splitted"
Column | Type | Collation | Nullable | Default
---------------+--------------------------+-----------+----------+---------
user_id | integer | | |
session_id | bigint | | not null |
timestamp | timestamp with time zone | | not null |
lat | double precision | | not null |
lon | double precision | | not null |
alt | double precision | | |
sampling_rate | timestamp with time zone | | |
Indexes:
"trajectories_splitted_pkey" PRIMARY KEY, btree (session_id, "timestamp")
"traj_splitted" btree (user_id, session_id, "timestamp")
您需要计算子查询中的值并
联接:
update trajectories_splitted ts
set sampling_rate = ts.timestamp - tts.prev_timestamp
from (select ts.*,
lag(timestamp) over (partition by user_id, session_id order by timestamp) as prev_timestamp
from trajectories_splitted ts
) tts
where tts.user_id = ts.user_id and tts.session_id = ts.session_id and
tts.timestamp = ts.timestamp
根据这个答案,postgres reports表达式的类型为interval
错误,如问题编辑中所示。@arilwan。这回答了您在这里提出的问题。您需要修复数据类型,以便可以存储所需的数据。谢谢,我已将列类型更改为interval
。找到了这个相关的答案