如何解决Oracle：基于变量和历史记录表获取价格
我有一个表“变量”和一个表“ variables_history”，如下所示
create table variables
(
variables_id number,variables_name varchar2(50),variables_value varchar2(50),variables_updated_at timestamp
);
create table variables_history
(
variables_id number,variables_hist_updated_at timestamp
);
历史记录是由触发器生成的，如下所示。
CREATE OR REPLACE EDITIONABLE TRIGGER "myuser"."trigger_variables_update"
AFTER UPDATE ON myuser.variables
REFERENCING NEW AS NEW OLD AS OLD
FOR EACH ROW
BEGIN
IF :old.variables_value <> :new.variables_value THEN
INSERT INTO myuser.variables_history
(variables_id,variables_name,variables_value,variables_hist_updated_at
VALUES
(variables_id,:old.variables_name,:old.variables_value,old.variables_updated_at);
END IF;
END trigger_variables_update;
我还有一张桌子，上面有所有的维护
create table maintenance
(
maintenance_id number,maintenance_status varchar2(20),maintenance_date timestamp
);
我需要基于maintenance_date的变量和variables_updated_at或variables_hist_updated_at
生成一个带有maintenance_price的输出像这样
WITH variables_data as
( SELECT 1 variables_id,'maintenance_price' variables_name,'30.00' variables_value,'2020-08-01 05:00:00.000' variables_updated_at from dual),variables_history_data as
(
SELECT 1 variables_id,'15.90' variables_value,'2019-10-01 11:30:00.000' variables_hist_updated_at from dual union all
SELECT 1 variables_id,'10.50' variables_value,'2020-01-01 01:00:00.000' variables_hist_updated_at from dual union all
SELECT 1 variables_id,'20.30' variables_value,'2020-05-01 12:30:00.000' variables_hist_updated_at from dual
),maintenance_data as
(
SELECT 1 maintenance_id,'COMPLETE' maintenance_status,'2019-02-01 00:30:00.000' maintenance_date from dual union all
SELECT 2 maintenance_id,'2019-05-01 01:30:00.000' maintenance_date from dual union all
SELECT 3 maintenance_id,'2019-11-01 02:30:00.000' maintenance_date from dual union all
SELECT 4 maintenance_id,'2020-07-10 05:30:00.000' maintenance_date from dual union all
SELECT 5 maintenance_id,'FAILED' maintenance_status,'2020-08-02 11:30:00.000' maintenance_date from dual
SELECT 6 maintenance_id,'2020-08-20 11:30:00.000' maintenance_date from dual
)
Select
m.maintenance_id,to_char(m.maintenance_date,'yyyy/mm/dd') as maintenance_date
v.variables_value
from
maintenances m
join variables v on m.maintenance_date >= v.variables_updated_at
join variables_history vh on m.maintenance_date < variables_hist_updated_at
where maintenance_status = 'COMPLETE';
这个查询只是一个例子，我知道它是错误的
我需要这样的输出（并考虑该变量可能具有新的更新）。 “ variable_value”必须是生成维护时的值。
maintenance_id | maintenance_date | variables_value |
---------------+------------------+-----------------+
1 | 2019-02-01| 15.90 |
---------------+------------------+-----------------+
2 | 2019-05-01| 15.90 |
---------------+------------------+-----------------+
3 | 2019-11-01| 10.50 |
---------------+------------------+-----------------+
4 | 2020-07-10| 20.30 |
---------------+------------------+-----------------+
6 | 2020-08-20| 30.00 |
---------------+------------------+-----------------+
解决方法
据我了解，您的数据（在Matthew McPeak的帮助下），历史记录表存储了价格过时的日期，而另一方面，“实时”表存储了价格生效的日期。
您可以通过两个横向连接来解决这个问题：
select
m.maintenance_id,to_char(m.maintenance_date,'yyyy/mm/dd') as maintenance_date,v.*,vh.*,coalesce(v.variables_value,vh.variables_value) as variables_value
from maintenances m
outer apply(
select v.variables_value
from variables_data v
where v.variables_updated_at <= m.maintenance_date
) v
outer apply (
select vh.variables_value
from variables_history_data vh
where vh.variables_hist_updated_at > m.maintenance_date
order by vh.variables_hist_updated_at
fetch first 1 row only
) vh
where m.maintenance_status = 'COMPLETE'
order by 1;
有关示例数据，the query returns：
MAINTENANCE_ID | MAINTENANCE_DATE | VARIABLES_VALUE
-------------: | :--------------- | --------------:
1 | 2019/02/01 | 15.9
2 | 2019/05/01 | 15.9
3 | 2019/11/01 | 10.5
4 | 2020/07/10 | null
6 | 2020/08/20 | 30
请注意，示例数据中存在故障。历史记录表中应有一行时间戳，该时间戳与实时数据的当前时间戳相对应-因此，maintenance_id 4与任何内容都不匹配。
您可以使用UNION ALL合并表，然后使用LAG / LEAD查找最新（或下一个）值：
SELECT *
FROM (
SELECT maintenance_id,COALESCE(
variables_value,LAG( variables_value,1 ) IGNORE NULLS OVER ( ORDER BY maintenance_date ),LEAD( variables_value,1 ) IGNORE NULLS OVER ( ORDER BY maintenance_date )
) AS variables_value,maintenance_date
FROM (
SELECT maintenance_id,NULL AS variables_value,maintenance_date
FROM maintenances
WHERE maintenance_status = 'COMPLETE'
UNION ALL
SELECT NULL,variables_value,variables_updated_at
FROM variables
UNION ALL
SELECT NULL,variables_hist_updated_at
FROM variables_history
)
)
WHERE maintenance_id IS NOT NULL;
其中，为您的示例数据：
CREATE TABLE variables ( variables_id,variables_name,variables_updated_at ) as
SELECT 1,'maintenance_price',30.00,TIMESTAMP '2020-08-01 05:00:00.000' from dual;
CREATE TABLE variables_history ( variables_id,variables_hist_updated_at ) as
SELECT 1,15.90,TIMESTAMP '2019-10-01 11:30:00.000' from dual union all
SELECT 1,10.50,TIMESTAMP '2020-01-01 01:00:00.000' from dual union all
SELECT 1,20.30,TIMESTAMP '2020-05-01 12:30:00.000' from dual;
CREATE TABLE maintenances ( maintenance_id,maintenance_status,maintenance_date ) as
SELECT 1,'COMPLETE',TIMESTAMP '2019-02-01 00:30:00.000' from dual union all
SELECT 2,TIMESTAMP '2019-05-01 01:30:00.000' from dual union all
SELECT 3,TIMESTAMP '2019-11-01 02:30:00.000' from dual union all
SELECT 4,TIMESTAMP '2020-07-10 05:30:00.000' from dual union all
SELECT 5,'FAILED',TIMESTAMP '2020-08-02 11:30:00.000' from dual union all
SELECT 6,TIMESTAMP '2020-08-20 11:30:00.000' from dual;
输出：
MAINTENANCE_ID | VARIABLES_VALUE | MAINTENANCE_DATE
-------------: | --------------: | :---------------------------
1 | 15.9 | 01-FEB-19 00.30.00.000000000
2 | 15.9 | 01-MAY-19 01.30.00.000000000
3 | 15.9 | 01-NOV-19 02.30.00.000000000
4 | 20.3 | 10-JUL-20 05.30.00.000000000
6 | 30 | 20-AUG-20 11.30.00.000000000
如果您交换LAG和LEAD（以选择下一个值而不是上一个值）：
SELECT *
FROM (
SELECT maintenance_id,variables_hist_updated_at
FROM variables_history
)
)
WHERE maintenance_id IS NOT NULL;
然后输出为：
MAINTENANCE_ID | VARIABLES_VALUE | MAINTENANCE_DATE
-------------: | --------------: | :---------------------------
1 | 15.9 | 01-FEB-19 00.30.00.000000000
2 | 15.9 | 01-MAY-19 01.30.00.000000000
3 | 10.5 | 01-NOV-19 02.30.00.000000000
4 | 30 | 10-JUL-20 05.30.00.000000000
6 | 30 | 20-AUG-20 11.30.00.000000000
db 提琴here
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