mysql - 此 SQL 查询是否会产生正确的结果？

Question

该查询旨在显示 tbltransactions 中按 customerid 分组的所有记录，并从 tblcustomers 中选择两个表的 customerid 匹配的客户名称。

select 
    a.customerid, 
    sum(transactionamount) as transactionamount, 
    b.customername 
from 
    tbltransactions a,
    tblcustomers b
where 
    a.customerid = b.customerid 
group by customerid 
order by b.customername

此查询是否确保 tbltransactions 中的所有记录都正确显示。我是 MySQL 和 php 新手。谢谢

其次:

当我添加“a”时。 to sum(transactionamount) as transactionamount"它会产生错误为什么会这样？此外它是什么类型的联接查询。

Answer 1

试试这个..

select a.customerid, sum(transactionamount) as transactionamount, b.customername from   tbltransactions a INNER JOIN tblcustomers b ON a.customerid = b.customerid group by customerid order by b.customername