MySQL：计算每行不同值的出现次数

Question

Based on an example already given, I would like to ask my further question. MySQL: Count occurrences of distinct values

example db

id         name
-----      ------
1          Mark
2          Mike
3          Paul
4          Mike
5          Mike
6          John
7          Mark

expected result

name       count
-----      -----
Mark       2
Mike       3
Paul       1
Mike       3
Mike       3
John       1
Mark       2

In my opinion 'GROUP BY' doesn't help. Thank you very much.

Answer 1

Simplest approach would be using Count() as Window Function over a partition of name ; but they are available only in MySQL 8.0.2 and onwards .

However, another approach is possible using a Derived Table . In a sub-select query (Derived Table), we will identify the counts for each unique name . Now, we simply need to join this to the main table, to show counts against each name (while not doing a grouping on them):

SELECT 
  t1.name, 
  dt.total_count 
FROM your_table AS t1 
JOIN 
(
 SELECT name, 
        COUNT(*) AS total_count 
 FROM your_table
 GROUP BY name
) AS dt ON dt.name = t1.name 
ORDER BY t1.id 

---

If MySQL 8.0.2+ is available, the solution would be less verbose:

SELECT 
  name, 
  COUNT(*) OVER (PARTITION BY name) AS total_count 
FROM your_table