[英]MySql query with multiple counts in result
我有一张桌子
create table posts (
text varchar(20),
created_at datetime,
user_id integer
);
create table users (
id integer,
name varchar(20),
important bolean
);
create table categories (
id integer,
name varchar(20),
);
create table categories_posts (
category_id integer,
post_id integer
);
想要计算特定时间之间每个类别的帖子数量,结果如下
START_TIME_PERIOD, category, count_all, count_important, count_normal
'2013-03-06 23:40', 'dogs', 20, 5, 15
'2013-03-06 23:40', 'cats', 22, 6, 16
'2013-03-06 23:40', 'birds', 24, 7, 17
其重要性取决于用户的重要性。
获得一个例如重要的计数
select '2013-03-06 23:40', categories.name, count(*)
from posts, users, categories
where posts.id = categories_posts.post_id
and categories.id = categories_posts.category_id
and posts.user_id = users.id
and users.important = true
and posts.created_at BETWEEN '2013-03-06 23:40' AND '2013-03-06 23:20'
group by 1, 2
在单个结果集中获取三个计数的最佳方法是什么?
谢谢
SELECT ..... , count(*), SUM(IF(user.important,1,0)) as count_important, COUNT(*) - SUM(IF(user.important,1,0)) as count_normal
您可以使用SUM
与CASE
结合使用,而不是使用COUNT
SELECT COUNT(*) AS count_all,
SUM(CASE WHEN important = 1 THEN 1 ELSE 0 END) AS count_important
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