如何在同一个语句中合并两个SUM查询？

Question

我有4个表：

employees 

emp-id | fname | lname 

------------- 

departments 

dep-id | dep-name 

------------- 

dep-emp 

emp-id | dep-id 

------------- 

salaries 

emp-id | salary 

我想编写一个程序，可以让用户输入2个数字，从这些部门的所有员工得到的工资相结合。

例

Enter department no: 6 
Enter second department no: 3 

背景计算

department 6 has 2 employees 
employee 1 earns 25,000 
employee 2 earns 22,000 
Total = 47,000 

department 3 has 3 employees 
employee 1 earns 40,000 
employee 2 earns 45,000 
employee 3 earns 35,000 
Total = 130,000 

Combined Total = 177,000 

输出：

Combined salary total for those departments is: 177,000 

我可以返回从员工SUM（工资）在一个部门，但我不能弄清楚如何总结两个部门，以及如何分配这两个程序正确输入。

这是我的程序至今：

CREATE PROCEDURE getDepartmentSalaryTotal(IN in_dep1 int(11), IN in_dep2 int(11)) 
SELECT SUM(salary) FROM salaries 
JOIN employees 
ON (salaries.emp-id = employees.emp-id) 
JOIN dep-emp 
ON (employees.emp-id = dep-emp.emp-id) 
WHERE dep-emp.dep-id = // in_dep1 + in_dep2; 

我不知道我是正确的接近它。

UPDATE

Java代码：

public static int getDepartmentSalaryTotal(Connection conn, int dep1, int dep2) { 
     int salaryTotal = 0; 
     try { 
      java.sql.PreparedStatement pst = conn.prepareStatement("{call getDepartmentSalaryTotal(?)}"); 
      pst.setInt(1, dep1); 
      pst.setInt(2, dep2); 

      ResultSet rs = pst.executeQuery(); 
      while (rs.next()){ 
       salaryTotal = rs.getInt(1); 
      } 
      rs.close(); 
      pst.close(); 
     } 
     catch (SQLException e) { 
      e.printStackTrace(); 
     } 
     return salaryTotal; 
    } 

任何帮助非常赞赏

Answer 1

您可以使用PreparedStatement执行以下查询：

select sum(salary) from salaries 
where emp_id in (select emp_id from dep_emp where dep_id in (?,?)); 

像这样：

PreparedStatement ps = connection.prepareStatement(above_sql_as_string); 

// To get total salary of 10 and 20 department_id: 
ps.setInt(1, 10); 
ps.setInt(2, 20); 

ResultSet rs = ps.executeQuery();