MySQL 具有特定值的 GROUP BY 并保持为 'other'

Question

我在用户注册时有一个 how did you hear about us? 表单域。现在通过收集的数据，我试图找到每个选项的百分比。我遇到的问题是任何已填写 other 的用户，我无法使用 group by 方法，因为他们输入了不同的内容。我如何将选项中没有的任何内容分组为 other?

user  |  how_heard
user1 |  facebook
user2 |  youtube
user3 |  facebook
user4 |  instagram
user5 |  advert
user6 |  facebook
user7 |  browsing the internet
user8 |  promotional tag
user9 |  university recommended me

最后三个用户，应分组为 other。我该怎么做？

这是我的查询，它有效但不适用于 other 中键入的值。

SELECT ma.how_heard
     , COUNT(1) AS total
     , COUNT(1) / t.cnt * 100 AS `percentage`
  FROM users ma
 CROSS
  JOIN (SELECT COUNT(1) AS cnt FROM users) t
 GROUP
    BY ma.how_heard
     , t.cnt

Answer 1

您可以使用 case 表达式：

SELECT 
    CASE WHEN u.how_heard IN ('facebook', 'youtube', 'instagram', 'advert')
        THEN u.how_heard
        ELSE 'other'
    END as how_heard_new,
    COUNT(*) AS total,
    COUNT(*) / t.cnt * 100 AS `percentage`
FROM users u 
CROSS JOIN (SELECT COUNT(*) AS cnt FROM users) t
GROUP BY how_heard_new, t.cnt

注意，如果你是运行 MySQL 8.0，你可以用window sum:

替换子查询

SELECT 
    CASE WHEN u.how_heard IN ('facebook', 'youtube', 'instagram', 'advert')
        THEN u.how_heard
        ELSE 'other'
    END as how_heard_new,
    COUNT(*) AS total,
    COUNT(*) / SUM(COUNT(*)) OVER() * 100 AS `percentage`
FROM users u 
GROUP BY how_heard_new

MySQL 具有特定值的 GROUP BY 并保持为 'other'

MySQL GROUP BY with specific values and remaining as 'other'

mysql

sql

case

count

aggregate-functions