Question

我有两列：一列与employee_id和一列与manager_id 除了employee_id为100的总裁没有经理（因此manager_id为null）之外，其余的还有经理。例如，总统是manager_id为100的两个人的经理。如何以这种方式计数和放置它： employee_id 100（column1）有2个下属（column2）？

尝试计数，求和，大小写，子查询并且不起作用

select employee_id,
       manager_id,
       first_name,
       last_name,
       case when employee_id = manager_id then count(employee_id) end,
       count(manager_id)
from   employees
--where manager_id is not null
group by manager_id,
       employee_id,
       first_name,
       last_name
--having sum(manager_id) > 5
order by employee_id;

我希望第一列为employee_id，第二列为每个employee_id计算的下属。

Answer 1

使用相关的分层查询：

Oracle设置：

RecyclerView

查询：

ArrayList<ModelClass> objModelClassArrayList;

public DatabaseRecyclerAdapter(ArrayList<ModelClass> objModelClassArrayList) {
    this.objModelClassArrayList = objModelClassArrayList;
}

@NonNull
@Override
public DatabaseViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType)
{
    View singleRow= LayoutInflater.from(parent.getContext()).inflate(R.layout.single_row,parent,false);
    return new DatabaseViewHolder(singleRow);

}

@Override
public void onBindViewHolder(@NonNull DatabaseViewHolder holder, int position)
{
    ModelClass objModelClass=objModelClassArrayList.get(position);
    holder.userNameTV.setText(objModelClass.getName());
    holder.userLocation.setText(objModelClass.getAddress());
    String e1=objModelClass.getEmail();
    holder.userEmail.setText(e1);


}


@Override
public int getItemCount() {
    return objModelClassArrayList.size();
}

public static class DatabaseViewHolder extends RecyclerView.ViewHolder
{

    TextView userNameTV,userLocation,userEmail;
    public DatabaseViewHolder(@NonNull View itemView)
    {
        super(itemView);
        userNameTV=itemView.findViewById(R.id.sr_userNameTV);
        userLocation=itemView.findViewById(R.id.sr_location);
        userEmail=itemView.findViewById(R.id.sr_email);
    }
}

输出：

EMPLOYEE_ID | NUM_SUBORDINATES
----------: | ---------------:
        100 |                9
        101 |                8
        102 |                2
        103 |                1
        104 |                0
        105 |                2
        106 |                1
        107 |                0
        108 |                1
        109 |                0

db <>提琴here

Answer 2

如果我了解您的问题，您也可以使用简单的分组依据来解决这将仅计入下属而不是整个层次

with tab as(
  select 1 as emp_id, null as man_id from dual union all
  select 2 as emp_id, 1 as man_id from dual union all
  select 3 as emp_id, 1 as man_id from dual union all    
  select 2 as emp_id, null as man_id from dual union all
  select 5 as emp_id, 2 as man_id from dual 
)

select man_id as employee_id
      , count(1) as cnt
from tab
where man_id is not null
group by man_id

EMPLOYEE_ID | CNT
----------: | --:
          2 |   1
          1 |   2

db <>提琴here

Answer 3

尝试一下：

-- data preparation
WITH EMPS AS 
(
SELECT 1001 AS EMP_ID, 'emp11' AS POS, 100 AS MGR_ID FROM DUAL UNION ALL
SELECT 1002 AS EMP_ID, 'emp12' AS POS, 100 AS MGR_ID  FROM DUAL UNION ALL
SELECT 1003 AS EMP_ID, 'emp13' AS POS, 100 AS MGR_ID  FROM DUAL UNION ALL
SELECT 2001 AS EMP_ID, 'emp21' AS POS, 200 AS MGR_ID  FROM DUAL UNION ALL
SELECT 2002 AS EMP_ID, 'emp22' AS POS, 200 AS MGR_ID  FROM DUAL UNION ALL
SELECT 100 AS EMP_ID, 'mgr1' AS POS, 1 AS MGR_ID  FROM DUAL UNION ALL
SELECT 200 AS EMP_ID, 'mgr2' AS POS, 1 AS MGR_ID  FROM DUAL UNION ALL
SELECT 1 AS EMP_ID, 'President' AS POS, NULL AS MGR_ID FROM DUAL )
-- Your actual query starts from here
SELECT
    EE.EMP_ID,
    EE.POS,
    EE.MGR_ID,
    CASE
        WHEN EC.CNT IS NULL THEN 0
        ELSE EC.CNT
    END AS CNT
FROM
    EMPS EE
    LEFT JOIN (
        SELECT
            MGR_ID,
            COUNT(1) AS CNT
        FROM
            EMPS
        GROUP BY
            MGR_ID
    ) EC ON EE.EMP_ID = EC.MGR_ID
ORDER BY
    EE.EMP_ID;

请根据您的需要添加其他条件。

DB Fiddle demo

Answer 4

尝试一下，在选择中使用选择

select emp.employee_id,
           emp.manager_id,
           emp.first_name,
           emp.last_name,
          (SELECT SUM(employees.employee_id) FROM employees where employees.manager_id=emp.employee_id) as subordinates,
           count(manager_id)
    from   employees emp

如何从同一表的manager_id中提取下属的数量？

4 个答案: