sql-使用 COUNT(*) OVER (PARTITION BY

我想创建一个新列，其中包含基于其他 3 列的重复元素的计数。当我尝试在 group by 上添加 i_count 时，我收到以下错误 SQL 状态：42P20。

SELECT
  cst,
  st,
  co,
  COUNT(*) OVER (PARTITION BY cst,st,co ) AS count
  --mean of loss by co
FROM s.tb_st , s.tb_cst , s.tb_co , erp.tb_i
WHERE st != 'te'
GROUP  BY cst,st ,co, count
ORDER BY cst , st, co;

输入

  cst          | st              |  co         

  sal          | pa              |  ctr          
  sal          | pa              |  ctr          
  sal          | pa              |  est          
  sal          | re              |  ctr         
  sal          | re              |  ctr          
  sal          | re              |  ust          
  cus          | pa              |  ctr          
  cus          | re              |  ctr          
  cus          | re              |  ctr          
  cus          | re              |  ctr          

预期产出

  cst          | st              |  co           |count | lossmeanbyco

  sal          | pa              |  ctr          | 2    | 2000
  sal          | pa              |  est          | 1    | 5000
  sal          | re              |  ctr          | 2    | 2000
  sal          | re              |  ust          | 1    | 1000
  cus          | pa              |  ctr          | 1    | 2000
  cus          | re              |  ctr          | 3    | 2000