查询各个部门的名称和员工个数

这个查询需要访问数据库，可以使用SQL语句实现。假设我们有两个表：一个是`Department`表，包含`id`和`name`两个字段；另一个是`Employee`表，包含`id`、`name`和`department_id`三个字段，其中`department_id`是外键，关联到`Department`表的`id`字段。

查询各个部门的名称和员工个数的SQL语句如下：

SELECT Department.name, COUNT(Employee.id) AS employee_count
FROM Department
LEFT JOIN Employee ON Department.id = Employee.department_id
GROUP BY Department.id

这个SQL语句使用了`LEFT JOIN`连接`Department`表和`Employee`表，并将它们按照`Department.id`分组。最后，使用`COUNT`函数统计每个部门的员工个数，并将结果命名为`employee_count`。

相关问题

mysql各个部门平均工资

根据引用中的查询结果，我们可以使用MySQL的GROUP BY语句来计算各个部门的总工资和总工时。为了计算各个部门的平均工资，我们需要将总工资除以该部门的总员工数。然后，我们可以使用平均工资的结果进行进一步的计算。请注意，具体的平均工资需要根据实际数据来计算。

问题: 请告诉我，MySQL各个部门的平均工资。<span class="em">1</span><span class="em">2</span><span class="em">3</span>
#### 引用[.reference_title]
- *1* [按部门统计各工资级别的人数、平均工资。](https://blog.csdn.net/weixin_34112863/article/details/113295625)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v93^chatsearchT3_1"}}] [.reference_item style="max-width: 50%"]
- *2* *3* [MySQL：查询每个部门的员工小时平均工资（显示部门名称、部门员工小时平均 工资）](https://blog.csdn.net/qq_40261735/article/details/104916127)[target="_blank" data-report-click={"spm":"1018.2226.3001.9630","extra":{"utm_source":"vip_chatgpt_common_search_pc_result","utm_medium":"distribute.pc_search_result.none-task-cask-2~all~insert_cask~default-1-null.142^v93^chatsearchT3_1"}}] [.reference_item style="max-width: 50%"]
[ .reference_list ]

Java完成一个企业人事管理系统，该系统中包含两个实体类:员工(Emp)，部门(Dept)，两个类中分别包含以下属性: 员工(工号，姓名，性别，职位，年龄，月薪，部门） 部门(编号，部门名，部门介绍，分机号) 要求实现以下功能: 完成部门的创建，添加3个部门 向各个部门中添加若干员工 查询所有的员工信息和所在的部门信息 根据员工工号显示员工信息 修改指定工号员工的薪资 根据部门号查询出门中的所有员工

下面是一个简单的 Java 代码示例，用于实现企业人事管理系统中的员工和部门功能。请注意，以下示例仅供参考，你可以根据自己的需求进行修改和扩展。

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Scanner;

class Employee {
    private int id;
    private String name;
    private String gender;
    private String position;
    private int age;
    private double salary;
    private int departmentId;

    public Employee(int id, String name, String gender, String position, int age, double salary, int departmentId) {
        this.id = id;
        this.name = name;
        this.gender = gender;
        this.position = position;
        this.age = age;
        this.salary = salary;
        this.departmentId = departmentId;
    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public String getGender() {
        return gender;
    }

    public String getPosition() {
        return position;
    }

    public int getAge() {
        return age;
    }

    public double getSalary() {
        return salary;
    }

    public void setSalary(double salary) {
        this.salary = salary;
    }

    public int getDepartmentId() {
        return departmentId;
    }
}

class Department {
    private int id;
    private String name;
    private String description;
    private int extensionNumber;

    public Department(int id, String name, String description, int extensionNumber) {
        this.id = id;
        this.name = name;
        this.description = description;
        this.extensionNumber = extensionNumber;
    }

    public int getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public String getDescription() {
        return description;
    }

    public int getExtensionNumber() {
        return extensionNumber;
    }
}

class HRManagementSystem {
    private List<Employee> employees;
    private Map<Integer, Department> departments;

    public HRManagementSystem() {
        employees = new ArrayList<>();
        departments = new HashMap<>();
    }

    public void createDepartment(int id, String name, String description, int extensionNumber) {
        Department department = new Department(id, name, description, extensionNumber);
        departments.put(id, department);
        System.out.println("部门创建成功！");
    }

    public void addEmployee(Employee employee) {
        employees.add(employee);
        System.out.println("员工添加成功！");
    }

    public void displayAllEmployees() {
        if (employees.isEmpty()) {
            System.out.println("暂无员工信息！");
        } else {
            System.out.println("所有员工信息：");
            for (Employee employee : employees) {
                System.out.println("工号：" + employee.getId());
                System.out.println("姓名：" + employee.getName());
                System.out.println("性别：" + employee.getGender());
                System.out.println("职位：" + employee.getPosition());
                System.out.println("年龄：" + employee.getAge());
                System.out.println("月薪：" + employee.getSalary());
                int departmentId = employee.getDepartmentId();
                Department department = departments.get(departmentId);
                System.out.println("部门编号：" + department.getId());
                System.out.println("部门名称：" + department.getName());
                System.out.println("--------------------");
            }
        }
    }

    public void displayEmployeeById(int id) {
        for (Employee employee : employees) {
            if (employee.getId() == id) {
                System.out.println("工号：" + employee.getId());
                System.out.println("姓名：" + employee.getName());
                System.out.println("性别：" + employee.getGender());
                System.out.println("职位：" + employee.getPosition());
                System.out.println("年龄：" + employee.getAge());
                System.out.println("月薪：" + employee.getSalary());
                int departmentId = employee.getDepartmentId();
                Department department = departments.get(departmentId);
                System.out.println("部门编号：" + department.getId());
                System.out.println("部门名称：" + department.getName());
                return;
            }
        }
        System.out.println("找不到指定工号的员工！");
    }

    public void modifyEmployeeSalary(int id, double newSalary) {
        for (Employee employee : employees) {
            if (employee.getId() == id) {
                employee.setSalary(newSalary);
                System.out.println("员工薪资修改成功！");
                return;
            }
        }
        System.out.println("找不到指定工号的员工！");
    }

    public void displayEmployeesByDepartmentId(int departmentId) {
        if (!departments.containsKey(departmentId)) {
            System.out.println("找不到指定部门！");
            return;
        }

        System.out.println("部门编号：" + departmentId);
        Department department = departments.get(departmentId);
        System.out.println("部门名称：" + department.getName());
        System.out.println("部门介绍：" + department.getDescription());
        System.out.println("分机号：" + department.getExtensionNumber());

        List<Employee> departmentEmployees = new ArrayList<>();
        for (Employee employee : employees) {
            if (employee.getDepartmentId() == departmentId) {
                departmentEmployees.add(employee);
            }
        }

        if (departmentEmployees.isEmpty()) {
            System.out.println("该部门暂无员工！");
        } else {
            System.out.println("部门员工信息：");
            for (Employee employee : departmentEmployees) {
                System.out.println("工号：" + employee.getId());
                System.out.println("姓名：" + employee.getName());
                System.out.println("性别：" + employee.getGender());
                System.out.println("职位：" + employee.getPosition());
                System.out.println("年龄：" + employee.getAge());
                System.out.println("月薪：" + employee.getSalary());
                System.out.println("--------------------");
            }
        }
    }
}

public class Main {
    public static void main(String[] args) {
        HRManagementSystem system = new HRManagementSystem();
        Scanner scanner = new Scanner(System.in);

        // 创建部门
        system.createDepartment(1, "技术部", "负责公司技术开发", 1001);
        system.createDepartment(2, "市场部", "负责公司市场拓展", 1002);
        system.createDepartment(3, "人事部", "负责公司人力资源管理", 1003);

        while (true) {
            System.out.println("请选择操作：");
            System.out.println("1. 添加员工");
            System.out.println("2. 查询所有员工信息");
            System.out.println("3. 根据员工工号显示员工信息");
            System.out.println("4. 修改指定工号员工的薪资");
            System.out.println("5. 根据部门号查询部门中的员工");
            System.out.println("0. 退出程序");

            int choice = scanner.nextInt();
            switch (choice) {
                case 1:
                    System.out.println("请输入员工信息：");
                    System.out.print("工号：");
                    int id = scanner.nextInt();
                    scanner.nextLine(); // 消耗换行符
                    System.out.print("姓名：");
                    String name = scanner.nextLine();
                    System.out.print("性别：");
                    String gender = scanner.nextLine();
                    System.out.print("职位：");
                    String position = scanner.nextLine();
                    System.out.print("年龄：");
                    int age = scanner.nextInt();
                    System.out.print("月薪：");
                    double salary = scanner.nextDouble();
                    System.out.print("部门编号：");
                    int departmentId = scanner.nextInt();
                    Employee employee = new Employee(id, name, gender, position, age, salary, departmentId);
                    system.addEmployee(employee);
                    break;
                case 2:
                    system.displayAllEmployees();
                    break;
                case 3:
                    System.out.print("请输入要查询的员工工号：");
                    int displayId = scanner.nextInt();
                    system.displayEmployeeById(displayId);
                    break;
                case 4:
                    System.out.print("请输入要修改薪资的员工工号：");
                    int modifyId = scanner.nextInt();
                    System.out.print("请输入新的薪资：");
                    double newSalary = scanner.nextDouble();
                    system.modifyEmployeeSalary(modifyId, newSalary);
                    break;
                case 5:
                    System.out.print("请输入要查询的部门编号：");
                    int departmentIdToDisplay = scanner.nextInt();
                    system.displayEmployeesByDepartmentId(departmentIdToDisplay);
                    break;
                case 0:
                    System.out.println("程序已退出。");
                    return;
                default:
                    System.out.println("无效的选择！");
                    break;
            }
        }
    }
}

这是一个简单的企业人事管理系统，你可以根据自己的需求进行修改和扩展。希望对你有帮助！如果还有其他问题，请随时提问。