如何编写一个查询来获取mysql中的计数

Question

我想获得今天的用户数和昨天的用户数量，我想只写一个查询我该怎么做...？

这些是我的查询我只想要一个查询：

SELECT COUNT(*) FROM visitors group by visited_date ORDER by visited_date DESC limit 1,1 as todayCount

SELECT COUNT(*) FROM visitors group by visited_date ORDER by visited_date DESC limit 1,0 as yesterdayCount

我的预期结果还是只有2列

todayCount yesterdayCount
     2          4

Answer 1

这应该做的伎俩：

SELECT COUNT(CASE 
                WHEN visited_date = CURDATE() THEN 1 
             END) AS todayCount ,
       COUNT(CASE 
                WHEN visited_date = CURDATE() - INTERVAL 1 DAY THEN 1 
             END) AS yesterdayCount 
FROM visitors  
WHERE visited_date IN (CURDATE(), CURDATE() - INTERVAL 1 DAY)
GROUP BY visited_date
ORDER by visited_date 

Answer 2

如果你知道当前和以前的日期，那么你可以这样做：

SELECT SUM(visited_date = CURDATE()) as today,
       SUM(visited_date = CURDATE() - interval 1 day) as yesterday
FROM visitors
WHERE visited_date >= CURDATE() - interval 1 day;

如果您不知道这两天，那么您可以做类似的事情，获取数据中的最新日期：

SELECT SUM(v.visited_date = m.max_vd) as today,
       SUM(v.visited_date < m.max_vd) as yesterday
FROM visitors v CROSS JOIN
     (SELECT MAX(v2.visited_date) as max_vd FROM visitors v2) as m
WHERE v.visited_date >= m.max_vd - interval 1 day

Answer 3

试试这个简单的查询

select visited_date as date, COUNT(*) as count from `visitors` 
group by `visited_date` order by `visited_date` asc

它会产生输出

它会对你有用。

Answer 4

试试这个：$ sqlToday =“选择COUNT（*）FROM menjava WHERE DATE（date_submitted）= CURRENT_DATE（）”;

$ sqlY yesterday =“选择COUNT（*）FROM menjava WHERE DATE（dc_created）= CURDATE（） - INTERVAL 1 DAY”;