計算組內的百分比

Question

給出一個表格，用於以下命令：

select sex, count(*) from my_table group by sex;
select sex, employed, count(*) from my_table group by sex, employed;

得到：

  sex  | count 
-------+------
male   | 1960 
female | 1801

和：

 sex     | employed | count 
---------+----------+-------
 male    | f        |  1523 
 male    | t        |   437 
 female  | f        |  1491 
 female  | t        |   310 

我在編寫查詢時遇到困難，該查詢將計算每個性別組中的就業百分比。 所以輸出應該如下所示：

 sex     | employed | count  | percent
---------+----------+--------+-----------
 male    | f        |  1523  | 77.7% (1523/1960)
 male    | t        |   437  | 22.3% (437/1960)
 female  | f        |  1491  | 82.8% (1491/1801)
 female  | t        |   310  | 17.2% (310/1801)

Answer 1

可能為時已晚，但對於即將到來的搜索者，可能的解決方案可能是：

select sex, employed, COUNT(*) / CAST( SUM(count(*)) over (partition by sex) as float)
  from my_table
 group by sex, employed

通過IO統計，這似乎是最有效的解決方案 - 可能取決於要查詢的行數 - 在上面的數字上測試...

同樣的態度可用於獲得男/女比例：

select sex, COUNT(*) / CAST( SUM(count(*)) over () as float)
  from my_table
 group by sex

此致，Jan

Answer 2

您可以使用子選擇和連接來執行此操作：

SELECT t1.sex, employed, count(*) AS `count`, count(*) / t2.total AS percent
  FROM my_table AS t1
  JOIN (
    SELECT sex, count(*) AS total 
      FROM my_table
      GROUP BY sex
  ) AS t2
  ON t1.sex = t2.sex
  GROUP BY t1.sex, employed;

我無法想到其他方法。