Question

我目前正在PostgreSQL服务器上工作。给定一个包含以下内容的表：

New Jersey | Male
New Jersey | Female
New York   | Male

我想返回看起来像这样的东西：

New Jersey | Male   | 2
New Jersey | Female | 2
New York   | Male   | 1

我基本上想知道表中有多少次新泽西州或纽约出现，无论它是男性还是女性。我也不想摆脱任何行。有什么解决办法吗？谢谢！

Answer 1

您需要窗口功能：

select t.*, count(city_name) over (partition by city_name)
from table t;

Answer 2

这应该做

SELECT state,
       gender,
       COUNT(1) OVER
         ( PARTITION BY state) fieldYouWant
  FROM Your_Table

Answer 3

以为您还可以使用子查询和聚合功能

   select distinct t1.*,t2.cnt as count from t t1
    inner join
    (
    select city_name, count(*) as cnt from t
    group by city_name
    ) as t2 on t1.city_name=t2.city_name

http://sqlfiddle.com/#!17/af578/1

city_name   gender  count
New York    Male    1
New Jersey  Female  2
New Jersey  Male    2

值出现的次数（sql）

3 个答案: