计算 MySQL 查询的百分比答案

【问题标题】：计算 MySQL 查询的百分比
【发布时间】：2022-01-23 15:56:50
【问题描述】：

我有一个查询，它返回一些数据计数如下，基本上这个表是posts 并且将包含inbound 或outbound 帖子。我想做一个查询，返回出站帖子的百分比。

例如

select count(*) as total, 
(select count(*) from posts where inbound = 0 and accountid = 333) as inbound,
(select count(*) from posts where inbound = 1 and accountid = 333) as outbound 
from account a
    join posts p on p.accountId = a.id where a.id = 333 
group by a.id;

这将返回类似以下内容...

+-------+---------+----------+
| total | inbound | outbound |
+-------+---------+----------+
|   802 |     525 |      277 |
+-------+---------+----------+

如何修改上面的查询，使其返回一个额外的列来计算总数的出站百分比，例如(277 / 802) * 100 例如(outbound / total) * 100)

那么结果中带有新列的预期输出将如下四舍五入到最接近的整数？

+-------+---------+----------+---------------------+
| total | inbound | outbound |  outboundPercentage |
+-------+---------+----------+---------------------+
|   802 |     525 |      277 |                  35 |
+-------+---------+----------+---------------------|

【问题讨论】：

标签： mysql sql

【解决方案1】：

我认为你可以使用最简单的方法：

with counts as (
  select 
    count(*) as total,
    count(nullif(inbound, 0)) as inbound,
    count(nullif(inbound, 1)) as outbound
  from posts
  where accountid = 333
) select 
    * ,
    round((outbound / total) * 100) outboundPercentage
from counts;

MySQL 8.0 fiddle

【讨论】：

super @Slave 正是我想很快接受的东西:)

【解决方案2】：

您可以简单地计算 sub query 和 join 与帐户的子查询中的帖子总数、入站总数、出站总数和百分比。

SELECT p.total,
       p.outbound,
       p.inbound,
       p.outboundPercentage
FROM `account` AS a
JOIN
  (SELECT accountid,
          COUNT(`id`) AS total,
          SUM(IF(inbound=1
                 AND accountid=333, 1, 0)) AS outbound,
          SUM(IF(inbound=0
                 AND accountid=333, 1, 0)) AS inbound,
          ROUND(((SUM(IF(inbound=1
                         AND accountid=333, 1, 0)) / COUNT(`id`)) * 100), 2) AS outboundPercentage
   FROM posts
   GROUP BY accountid) AS p ON p.accountid = a.id
WHERE a.id = 333
GROUP BY a.id

【讨论】：