如何在PostgreSQL中计算单列值占比：tech_support列Yes/No占比

直接用下面的查询语句就能生成你要的占比统计表：

SELECT
  s.tech_support,
  COUNT(*) AS customer_count,
  ROUND(COUNT(*) * 100.0 / SUM(COUNT(*)) OVER (), 2) AS percentage
FROM customer AS c
JOIN location AS l ON c.location_id = l.location_id
JOIN services AS s ON c.customer_id = s.customer_id
WHERE age > 25 AND age < 42 AND state = 'NC'
GROUP BY s.tech_support;

语句说明： #

• GROUP BY s.tech_support：按tech_support的Yes/No分组统计
• COUNT(*)：统计每组的客户数量
• SUM(COUNT(*)) OVER ()：计算符合条件的总客户数，窗口函数OVER()表示不分组，取全局总和
• ROUND(..., 2)：把占比保留两位小数，转成百分比格式

执行后会得到三列：tech_support的值、对应客户数、占比（百分比），直接就是你要的统计结果。

内容的提问来源于stack exchange，提问作者blaxmyth