如何在同一個語句中合併兩個SUM查詢？

Question

我有4個表：

employees 

emp-id | fname | lname 

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

departments 

dep-id | dep-name 

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

dep-emp 

emp-id | dep-id 

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

salaries 

emp-id | salary 

我想編寫一個程序，可以讓用戶輸入2個數字，從這些部門的所有員工得到的工資相結合。

例

Enter department no: 6 
Enter second department no: 3 

背景計算

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 

輸出：

Combined salary total for those departments is: 177,000 

我可以返回從員工SUM（工資）在一個部門，但我不能弄清楚如何總結兩個部門，以及如何分配這兩個程序正確輸入。

這是我的程序至今：

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; 

我不知道我是正確的接近它。

UPDATE

Java代碼：

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; 
    } 

任何幫助非常讚賞

Answer 1

您可以使用PreparedStatement執行以下查詢：

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

像這樣：

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();