根据table2选择table1中列的总和？

Question

我有两个表，员工和交易，如下所示：

 employees: 
 EmployeeID
 firstname
 lastname

 transactions: 
 TransactionID
 employeeID
 amount

我如何获得名为'John'的所有员工的总额'？谢谢！

 Select sum(amount) 
 from transactions 
 where employeeID = (everyone with first name John)

Answer 1

您只需要执行JOIN：

Select  Sum(T.Amount)
From    Transactions    T
Join    Employees       E   On  E.EmployeeId = T.EmployeeId
Where   E.FirstName = 'John'

Answer 2

尝试：

Select sum(amount)
from transactions
where employeeID 
   in (Select employeeID from employees 
       where firstname ='firstname');

thx;）

Answer 3

你快到了。尝试：

SELECT SUM(amount) 
FROM transactions t
INNER JOIN employees e
    ON t.employeeID = e.employeeID
WHERE e.firstName = 'John'

或者，这也适用

SELECT SUM(amount) 
FROM transactions t
WHERE t.employeeId IN (
    SELECT employeeID
    FROM employees e
    WHERE e.firstName = 'John'
    )

Answer 4

INNER JOIN应该可以解决问题。看看下面提供的查询：

SELECT SUM(T.amount) FROM
Transactions T INNER JOIN Employees E
ON T.EmployeeID = E.EmployeeID
WHERE E.FirstName = 'John'

Answer 5

这是我的猜测。您必须将两个表连接在一起，然后过滤所需的数据。

SELECT     SUM(tr.amount)
FROM       Employees emp
INNER JOIN transactions tr ON emp.employeeId = tr.EmployeeId
WHERE      emp.FirstName = 'John'