[英]How to Choose a specific value from a table and to avoid duplicates?
我有两个表:
主表
id AccountNum status
1 11001 active
2 11002 active
3 11003 active
4 11004 active
添加表
id date description
1 01.2020 ACCOUNT.SET
1 02.2020 ACCOUNT.CHANGE
1 03.2020 ACCOUNT.REMOVE
2 04.2020 ACCOUNT.SET
2 05.2020 ACCOUNT.CHANGE
3 08.2020 ACCOUNT.SET
4 05.2020 ACCOUNT.SET
4 09.2020 ACCOUNT.REMOVE
我需要得到这样的结果:
EffectiveFrom是设置 Account 的日期, EffectiveTo是删除 Account 的日期
id AccountNum EffectiveFrom EffectiveTo
1 11001 01.2020 03.2020
2 11002 04.2020 null
3 11003 08.2020 null
4 11004 05.2020 09.2020
问题是,在加入 AddTable 后,我得到了重复项,但我只需要每个 Id 上的一行,并且只需要 ACCOUNT.SET、ACCOUNT.REMOVE 中的描述的日期。
您在寻找left join
吗?
select m.id as id,
m.AccountNum as AccountNum,
a.date as EffectiveFrom,
b.date as EffectiveTo
from MainTable m left join
AddTable a on (a.id = m.id and a.description = 'ACCOUNT.SET') left join
AddTable b on (b.id = m.id and b.description = 'ACCOUNT.REMOVE')
order by m.AccountNum
使用PIVOT
和LEFT OUTER JOIN
:
SELECT m.id,
a.EffectiveFrom,
a.EffectiveTo
FROM MainTable m
LEFT OUTER JOIN
(
SELECT *
FROM AddTable
PIVOT( MAX( dt ) FOR description IN (
'ACCOUNT.SET' AS EffectiveFrom,
'ACCOUNT.REMOVE' AS EffectiveTo
) )
) a
ON ( a.id = m.id )
ORDER BY m.id
所以对于你的测试数据:
CREATE TABLE MainTable ( id, AccountNum, status ) AS
SELECT 1, 11001, 'active' FROM DUAL UNION ALL
SELECT 2, 11002, 'active' FROM DUAL UNION ALL
SELECT 3, 11003, 'active' FROM DUAL UNION ALL
SELECT 4, 11004, 'active' FROM DUAL;
CREATE TABLE AddTable ( id, dt, description ) AS
SELECT 1, DATE '2020-01-01', 'ACCOUNT.SET' FROM DUAL UNION ALL
SELECT 1, DATE '2020-01-02', 'ACCOUNT.CHANGE' FROM DUAL UNION ALL
SELECT 1, DATE '2020-01-03', 'ACCOUNT.REMOVE' FROM DUAL UNION ALL
SELECT 2, DATE '2020-01-04', 'ACCOUNT.SET' FROM DUAL UNION ALL
SELECT 2, DATE '2020-01-05', 'ACCOUNT.CHANGE' FROM DUAL UNION ALL
SELECT 3, DATE '2020-01-08', 'ACCOUNT.SET' FROM DUAL UNION ALL
SELECT 4, DATE '2020-01-05', 'ACCOUNT.SET' FROM DUAL UNION ALL
SELECT 4, DATE '2020-01-09', 'ACCOUNT.REMOVE' FROM DUAL;
这输出:
\n身份证 | 效果自 | 有效于\n -: | :------------ | :----------\n 1 | 01-JAN-20 | 03-JAN-20 \n 2 | 04-JAN-20 | 空值 \n 3 | 08-JAN-20 | 空值 \n 4 | 05-JAN-20 | 09-JAN-20 \n
db<> 在这里摆弄
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