在sql

Question

我有下表，我想写一个优化的查询：

Id   Name      Department
--------------------------------
 1   Ojas      Soft Engineer    
 2   Amy       Marketing        
 3   Aditya    Networking      
 4   Riya      Admin      
 5   Ojas      Manager      
 6   Riya      Receptionist

我需要输出：

Id   Name      Department     Name repeat count
------------------------------------------------
 1   Ojas      Soft Engineer           2
 2   Amy       Marketing               1
 3   Aditya    Networking              1
 4   Riya      Admin                   2
 5   Ojas      Manager                 2
 6   Riya      Receptionist            2

我的查询：

SELECT
    Id, Name, Department, COUNT(*) as RepeatNameCount
FROM
    Email
GROUP BY
    Name

但我想要返回每一行。我的问题有时在网格中只返回10行，但是对于所有可用数据，应返回重复的名称数

Answer 1

另一个选项是窗口功能

Select *
      ,RepeatCnt = sum(1) over (partition by Name) 
 From Email

  

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Answer 2

您可以在子查询上使用具有受约束结果的连接

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Answer 3

您可以使用窗口功能或subquery

select *,
        count(*) over (partition by name) RepeatNameCount  
from email e;

或者您也可以使用subsquery

select *,
        (select count(*) from email where name = e.name) RepeatNameCount  
from email e;

Answer 4

选择ID，姓名，部门，          （从电子邮件x中选择计数（*），其中x.name = y.name group by x.name）为Repeat_Name_Count 来自电子邮件y;