SQL許多一對多計數總和

Question

我有這個表：

id_user id_user2 
1  54 
1  53 
1  53 
1  54 
1  54 
1  55 
2  23 
2  23 
2  20 
2  21 
2  25 
2  25 

，我想來算，怎麼id_user許多都設有帶id_user2關係。輸出應該是：

id_user id_user2 result 
1  54   3 
1  53   2 
1  55   1 
2  23   2 
2  20   1 
2  21   1 
2  25   2 

Answer 1

你必須使用group by條款

select id_user,id_user2, count(1) as result 
from userstab 
group by id_user,id_user2 

Answer 2

嘗試此查詢

select id_user,id_user2,count(id_user2) as result 
from TABLE_NAME group by id_user2