MYSQL 计数 - 如果为空则返回 0

Question

这是我的查询:

select COUNT(*) as total, COUNT(distinct user) as unique 
FROM table 
WHERE uristem in ('/example/', '/example/', '/example/', '/example/') 
      and time > DATE_SUB(NOW(), INTERVAL 24 HOUR)' 
group by uristem;

应该是这样的

100 50
25  50
0   0
100 35

但是如果没有计数，它看起来像这样(缺失)

100 50
40  50
100 35

如何填写 0？

Answer 1

试试这个(未经测试):

select COUNT(t.uristem) as total
, COUNT(distinct t.user) as unique 
FROM 
    (
        select uristem, user
        from table
        where time > DATE_SUB(NOW(), INTERVAL 24 HOUR) 
    ) t
right outer join 
(
    select '/example/' x
    union select '/example/'
    union select '/example/'
    union select '/example/'
) y
on t.uristem = y.x
group by y.x;