题目
表: Users
+--------------+---------+ | Column Name | Type | +--------------+---------+ | account | int | | name | varchar | +--------------+---------+ account 是该表的主键. 表中的每一行包含银行里中每一个用户的账号.
表: Transactions
+---------------+---------+ | Column Name | Type | +---------------+---------+ | trans_id | int | | account | int | | amount | int | | transacted_on | date | +---------------+---------+ trans_id 是该表主键. 该表的每一行包含了所有账户的交易改变情况. 如果用户收到了钱, 那么金额是正的; 如果用户转了钱, 那么金额是负的. 所有账户的起始余额为 0.
写一个 SQL, 报告余额高于 10000 的所有用户的名字和余额. 账户的余额等于包含该账户的所有交易的总和.
返回结果表单没有顺序要求.
查询结果格式如下例所示.
Users table: +------------+--------------+ | account | name | +------------+--------------+ | 900001 | Alice | | 900002 | Bob | | 900003 | Charlie | +------------+--------------+ Transactions table: +------------+------------+------------+---------------+ | trans_id | account | amount | transacted_on | +------------+------------+------------+---------------+ | 1 | 900001 | 7000 | 2020-08-01 | | 2 | 900001 | 7000 | 2020-09-01 | | 3 | 900001 | -3000 | 2020-09-02 | | 4 | 900002 | 1000 | 2020-09-12 | | 5 | 900003 | 6000 | 2020-08-07 | | 6 | 900003 | 6000 | 2020-09-07 | | 7 | 900003 | -4000 | 2020-09-11 | +------------+------------+------------+---------------+ Result table: +------------+------------+ | name | balance | +------------+------------+ | Alice | 11000 | +------------+------------+ Alice 的余额为(7000 + 7000 - 3000) = 11000. Bob 的余额为1000. Charlie 的余额为(6000 + 6000 - 4000) = 8000.
解题
select u.name, sum(t.amount) as balance from Users as u left join Transactions as t on u.account=t.account group by u.name having balance>10000;
