分組資料

指定分組後，對每個分組裡的資料進行聚集

1. select vend_id, count(*) as num_prods from products group by vend_id;

2. 過濾分組
   select cust_id, count(*) from orders group by cust_id having count(*) > =2;

注意： where是在分組前進行過濾，having是在分組後進行過濾

1. 價格>=10, 具有2個產品及其以上的供應商。
   select vend_id, count(*) as num_prods from products where prod_price >=10 group by vend_id having count(*) >=2;

2. 總計訂單價格大於等於50的訂單號和總計價格
   select order_num, sum(quantity * item_price) as ordertotal from orderitems group by order_num having sum(quantity * item_price) >=50;

3. select order_num, sum(quantity * item_price) as ordertotal from orderitems group by order_num having sum(quantity * item_price) >=50 order by ordertatal