本文介紹了Oracle SQL -- 合并兩個表，但從一個表中提取重復項?的處理方法，對大家解決問題具有一定的參考價值，需要的朋友們下面隨著小編來一起學習吧！
問題描述
限時送ChatGPT賬號..
我有這些表:
Table A
Num Letter
1 A
2 B
3 C
Table B
Num Letter
2 C
3 D
4 E
我想聯合這兩個表，但我只希望每個數字出現一次.如果兩個表中出現相同的數字，我希望它來自表 B 而不是表 A.
I want to union these two tables, but I only want each number to appear once. If the same number appears in both tables, I want it from Table B instead of table A.
Result
Num Letter
1 A
2 C
3 D
4 E
我怎么能做到這一點?聯合將保留重復項，而相交將僅捕獲相同的行——當它具有相同的數字時，我認為一行是重復的，而不管字母如何.
How could I accomplish this? A union will keep duplicates and an intersect would only catch the same rows -- I consider a row a duplicate when it has the same number, regardless of the letter.
推薦答案
還有一個:
SELECT COALESCE(b.num, a.num) num, COALESCE(b.letter, a.letter) letter
FROM a FULL JOIN b ON a.num = b.num
ORDER BY 1;
使用您的數據:
WITH a AS
(SELECT 1 num, 'A' letter FROM dual
UNION ALL SELECT 2, 'B' FROM dual
UNION ALL SELECT 3, 'C' FROM dual),
b AS
(SELECT 2 num, 'C' letter FROM dual
UNION ALL SELECT 3, 'D' FROM dual
UNION ALL SELECT 4, 'E' FROM dual)
SELECT COALESCE(b.num, a.num) num, COALESCE(b.letter, a.letter) letter
FROM a FULL JOIN b ON a.num = b.num
ORDER BY 1;
NUM L
---------- -
1 A
2 C
3 D
4 E
這篇關于Oracle SQL -- 合并兩個表，但從一個表中提取重復項?的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！
【網站聲明】本站部分內容來源于互聯網,旨在幫助大家更快的解決問題，如果有圖片或者內容侵犯了您的權益，請聯系我們刪除處理，感謝您的支持！