mysql - 最大事务的sql查询

Question

我有一个这样的表

我要选择Acct_id，已完成最大交易数的用户的交易数。

select Acct_id,max(num) From (select Acct_id, count(Acct_id) as num from Transactions group by Acct_id);

我上面的 sql 查询给我错误- 每个派生表都必须有自己的别名

why my query was being fail without Alias?

Answer 1

您的查询必须是:-

SELECT Acct_id, MAX(num) 
FROM (SELECT Acct_id, COUNT(Acct_id) AS num 
      FROM Transactions 
      GROUP BY Acct_id) TAB;