選擇訂購了最大數量產品的客戶？

Question

我正在試圖查詢以查找從下表中訂購了最大數量的產品的客戶！

mysql> select * from ORDERS; 
+---------+---------+------------+-----+ 
| CUSTNUM | PRODNUM | DATE  | QTY | 
+---------+---------+------------+-----+ 
| 125216 | 2323 | 2016-03-21 | 2 | 
| 136101 | 2357 | 2016-03-21 | 5 | 
| 136101 | 2357 | 2016-10-12 | 1 | 
| 136101 | 2357 | 2016-11-25 | 5 | 
| 136101 | 3737 | 2016-10-12 | 10 | 
| 136101 | 9193 | 2016-11-25 | 5 | 
| 182764 | 2357 | 2015-03-21 | 12 | 
| 182764 | 2357 | 2016-05-12 | 10 | 
| 212836 | 3737 | 2015-09-16 | 6 | 
| 455566 | 4143 | 2016-02-09 | 10 | 
| 455566 | 4143 | 2016-05-12 | 10 | 
+---------+---------+------------+-----+ 

預期的結果事先求助

+-------------+------------------+ 
| CUSTNUM  | quantity_ordered | 
+-------------+------------------+ 
| 136101  |    26 | 
+-------------+------------------+ 

感謝。

Answer 1

使用group by子句。

欲瞭解更多信息， 請參考一些tutorials

或讀official docs

SELECT CUSTNUM, SUM(QTY) s FROM ORDERS GROUP BY CUSTNUM 
ORDER BY s DESC LIMIT 1 

SQLfiddle