[英]How do I query SQL for the latest record based on latest Date and Time OR Date_Time columns?
[英]How to get the latest date time record in an sql query with a where clause?
我有两个表: RO_LAMEL_DATA
和RO_MAIN_TABLE
。 RO_MAIN_TABLE
包括具有记录键 ( record_key
) 的产品的所有序列号 ( serial_nr
)。 RO_LAMEL_DATA
为每个记录键(例如机器状态( machine_status
)和日期时间值( pr_date_time
)有几条记录(在同一天)。 我想获得一个生产的最新机器状态。 为此,我这样做:
select a.machine_status
from ro_lamel_Data a inner join (
select record_key, max(pr_date_time) as MaxDate
from ro_lamel_Data
group by record_key
) ro_main_table on (a.record_key = ro_main_table.record_key) and a.pr_date_time = MaxDate
where a.record_key =(
select record_key from ro_main_table where serial_nr = 'Y39489');
但是我得到了错误:
单行子查询返回多于一行
我该如何解决这个问题? 提前致谢!
也许你需要类似的东西
WITH cte AS ( SELECT machine_status,
record_key,
ROW_NUMBER() OVER (PARTITION BY record_key
ORDER BY pr_date_time DESC) rn
FROM ro_lamel_Data )
SELECT cte.record_key, cte.machine_status last_status
FROM cte
JOIN ro_main_table ON cte.record_key = ro_main_table.record_key
WHERE rn = 1
如果你想要一行,使用order by
和fetch first
:
select ld.machine_status
from ro_lamel_Data ld join
ro_main_table mt
using (record_key)
where mt.serial_nr = 'Y39489'
order by ld.pr_ate_time desc
fetch first 1 row only;
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