MYSQL sum/Count在内部联接组内失败

Question

我有一个包含销售记录的表：

员工2空

销售ID	EmployeeId(FK(
1	101	空
2	102
3	300	Bob

您可以在两个条件中的任何一个条件下连接表，并使用条件聚合：

SELECT e.employee_id, 
e.employee_Name, 
SUM(s.employee_id = e.employee_id) AS saleCount, 
SUM(CASE WHEN s.employee_id = e.employee_id THEN s.grand_total ELSE 0 END) AS totalSalesRevenue, 
SUM(s.employee2 = e.employee_Name) AS helperEmpCount
FROM employee e LEFT JOIN sale s
ON s.employee_id = e.employee_id OR s.employee2 = e.employee_Name
GROUP BY e.employee_id;