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[英]MySQL: Select all rows with the same ID, if a column from a joined table contains x
[英]How can I select rows with an extra column joined from the same table
我有一張這樣的桌子:
id | path | name | date | data
---+-----------+------+------------+-----
1 | Docs | 1000 | 2022-01-01 | aaa0
2 | Docs/1000 | Text | 2022-01-11 | AAA0
3 | Docs | 1001 | 2022-02-02 | aaa1
4 | Docs/1001 | Text | 2022-02-12 | AAA1
我怎樣才能 select 路徑為“文檔”的所有行並添加相應“文本”的日期,即:
id | path | name | date | date_of_text | data
---+------+------+------------+--------------+-----
1 | Docs | 1000 | 2022-01-01 | 2022-01-11 | AAA0
3 | Docs | 1001 | 2022-02-02 | 2022-02-12 | AAA1
您可以通過自連接實現預期的結果 -
SELECT T1.id, T1.path, T1.name, T1.date, T2.date date_of_text, T2.data
FROM table_name T1
LEFT JOIN table_name T2 ON T1.name = SUBSTRING(path, POSITION("/" IN path) + 1, LENGTH(path))
WHERE T1.path = 'Docs'
有很多方法可以做到這一點,包括
相關子查詢
select t.*,id % 2 ,(select date from t t1 where t1.ID = t.id + 1) datetext
from t
where id % 2 > 0;
自我加入
select t.*,t.id % 2 , t1.date
from t
join t t1 on t1.ID = t.id + 1
where t.id % 2 > 0;
聚合
select min(id) id,min(path) path,min(date) date,upper(data) data ,max(date) datetext
from t
group by t.data;
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