select order_num from orderitems where prod_id =
'rgan01'
;select cust_id from orders where order_num in
(20007
,20008);
##結合兩句查詢
select cust_id from orders where order_num in
(select order_num from orderitems where prod_id =
'rgan01');
select cust_name, cust_contact from customers where cust_id in
(select cust_id from orders where order_num in
(select order_num from orderitems where prod_id =
'rgan01'))
;select
count(*
)as orders from orders where cust_id =
1000000001
;select cust_name,
cust_state,
(select
count(*
)from orders
where orders.cust_id = customers.cust_id)
as orders
from customers
order
by cust_name;
## 錯誤例子
select cust_name,
cust_state,
(select
count(*
)from orders
where cust_id = cust_id)
as orders -- 錯誤，因為沒有限制列名
from customers
order
by cust_name;
## challenges
select cust_id from orders where order_num in
(select order_num from orderitems where item_price >=10)
;-- 1
select cust_id,
order_date
from orders
where cust_id in
(select cust_id from orderitems where prod_id =
'br01'
)order
by order_date;
-- 2
select cust_email
from customers
where cust_id in
(select cust_id from orders where cust_id in
(select cust_id from orderitems where prod_id =
'br01'))
;-- 3
## 第四題
select cust_id,
(select
sum(quantity * item_price)
-- sum和括號中不要有空格
from orderitems
where orderitems.order_num = orders.order_num
group
by order_num)
as total_ordered-- 第二步選出**
from orders
order
by total_ordered;
-- 第一步選出顧客id
## 第五題
select prod_name,
(select
sum(quantity)
from orderitems
where orderitems.prod_id = products.prod_id
group
by prod_id)
as quant_sold -- 找出賣掉的產品數量
from products;
-- 找出對應的產品名稱
子查詢只能查詢單列
列名要完全限定，錯誤例子見**
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