LeetCode（数据库）- 顾客的可信联系人数量

Posted 2021-10-06 程序员牧码

题目链接：点击打开链接

题目大意：略。

解题思路：略。

AC 代码

-- 解决方案(1)
WITH t1 AS(SELECT customer_id, customer_name, COUNT(contact_name) contacts_cnt, COUNT(IF(contact_email IN (SELECT email FROM Customers), 1, null)) trusted_contacts_cnt
FROM Customers cu LEFT JOIN Contacts co ON customer_id = user_id 
GROUP BY customer_id)

SELECT invoice_id, customer_name, price, contacts_cnt, trusted_contacts_cnt
FROM t1 JOIN Invoices inv ON inv.user_id = customer_id
ORDER BY invoice_id

-- 解决方案(2)
SELECT invoices.invoice_id, customers.customer_name, invoices.price, COUNT(contacts.user_id) AS contacts_cnt, COUNT(c2.email) AS trusted_contacts_cnt
FROM Invoices invoices
INNER JOIN Customers customers ON invoices.user_id = customers.customer_id
LEFT JOIN Contacts contacts ON customers.customer_id = contacts.user_id
LEFT JOIN Customers c2 ON contacts.contact_email = c2.email
GROUP BY invoices.invoice_id
ORDER BY invoices.invoice_id