顯示最新修改的記錄爲每個員工

Question

EMP表作爲這樣

id  Name    Date Modified 
1  Ram    2017-01-05 
2  Kishore   2017-02-04 
3 John    2017-04-22 
1 Ram K    2017-04-25 
1 Ram Kumar   2017-05-01 
2 Kishore Babu  2017-05-05 
3 John B   2017-06-01 

Answer 1

假設你正在使用一個合理rdbms支持窗口功能，row_number應該做的伎倆：

SELECT id, name, date_modified 
FROM (SELECT id, name, date_modified, 
       ROW_NUMBER() OVER (PARTITION BY id ORDER BY date_modified DESC) rn 
     FROM emp) t 
WHERE rn = 1