如何在DB2中分組並獲取每個組中的第一項？

Question

我有這樣一個表：

|sub_account|name|email| 
|-----------|----|-----| 
// same account and same name: email different 
|a1   |n1 |e1 | 
|a1   |n1 |e2 | 
// same account, name and email 
|a2   |n2 |e3 | 
|a2   |n2 |e3 | 

我想查詢來獲取這樣的表格：

|sub_account|name|email| 
|-----------|----|-----| 
// nothing to do here 
|a1   |n1 |e1 | 
|a1   |n1 |e2 | 
// remove the one that is exactly the same, but leave at least one 
|a2   |n2 |e3 | 

我已經試過：

select sub_account, name, first(email) 
from table 
group by sub_account, name 

但你知道「第一個」在DB2中不存在;它有什麼選擇？

感謝

Answer 1

select sub_account, name, email 
from table 
group by sub_account, name, email 

Answer 2

我不知道在DB2中。在SQL服務器中，您可以針對您的問題使用DISTINCT ..您可以嘗試。

SELECT DISTINCT sub_acount, name, email 
from TABLE 

Answer 3

我找到了一種方法：

SELECT sub_account, 
     name, 
     CASE WHEN split_index=0 THEN MyList ELSE SUBSTR(MyList,1,LOCATE('|',MyList)-1) END 
FROM (select sub_account, name, LISTAGG(email,'|') as MyList, LOCATE('|',LISTAGG(LB_ARTICLE_CAISSE,'|')) AS split_index 
     from TABLE 
     group by sub_account, name) AS TABLEA 

此功能將收集您的郵件和分裂後，採取的第一個