Question

我有两张桌子

table:user
user_id   int
desc      varchar(255)


table:task
task_id        int
user_id    int
create_time datetime

我想得到desc =＆＃34; sth＆＃34;在今天＆amp; amp;昨天，所以我这样写了。

select u.user_id, today_task_count, yesterday_task_count
from user as u
inner join (
    select user_id,
    SUM(case when DATE(create_time) = CURDATE() then 1 else 0 end) as       today_task_count 
    SUM(case when DATE(create_time) = CURDATE()-1 then 1 else 0 end) as       yesterday_task_count
    from task
    group by user_id
) as t
On u.user_id = t.task_id
where u.desc = 'sth'

或

On u.user_id = t.task_id AND u.desc = 'sth'

但是他们都扫描了表格任务中的所有记录。我该如何改进呢...... 我知道有一些问题像这样问过，但我仍然无法在我的场景中找到解决方案。

=========================更新===================== ======= 现在我使用jWeaver的anwer

select u.user_id, 
SUM(case when DATE(create_time) = CURDATE() then 1 else 0 end) as       today_task_count
SUM(case when DATE(create_time) = CURDATE()-1 then 1 else 0 end) as       yesterday_task_count
from (SELECT * FROM user where desc = 'sth') as u   for desc='sth' 
inner join task as t
On u.user_id = t.task_id
group by u.user_id

对于desc条件它没问题，但它需要花费4秒钟，而我的第一个sql需要2秒才能完成，总和操作会有更多这样的痛苦吗？

Answer 1

我认为这些SQL对你有用。

select u.user_id, count(*)
from user as u
inner join (
    select user_id
    from task
    group by user_id
) as t
On u.user_id = t.task_id
AND u.desc = 'sth' and  DATE(create_time) = CURDATE()

这些查询给出了今天的计数和昨天的计数

select user.user_id, today_task_count, yesterday_task_count
from
 ( SELECT * FROM user where desc = 'sth' ) as user  
 join
 ( select user_id,
    SUM(case when DATE(create_time) = CURDATE() then 1 else 0 end) as   today_task_count ,
     SUM(case when DATE(create_time) = DATE_SUB(CURDATE(), INTERVAL 1 DAY)then 1 else 0 end) as   yesterday_task_count 
    from task
    group by user_id
   ) as task
On user.user_id = task.task_id

谢谢。

Answer 2

好像你正在寻找这个..

select u.user_id, today_task_count
from (SELECT * FROM user where desc = 'sth') as u  --- filter you table for desc='sth' 
inner join (
    select user_id,
    SUM(case when DATE(create_time) = CURDATE() then 1 else 0 end) as       today_task_count 
    from task
    group by user_id
) as t
On u.user_id = t.task_id

<强> ===更新===

select u.user_id, SUM(case when DATE(create_time) = CURDATE() then 1 else 0 end) as       today_task_count
    from (SELECT * FROM user where desc = 'sth') as u  --- filter you table for desc='sth' 
    inner join task as t
    On u.user_id = t.task_id
     group by u.user_id

Answer 3

我不知道你为什么要尝试复杂的查询只是尝试这个，你会得到所需的结果：

select user.user_id,count(create_time) as today_task_count from task left join user on user.user_id=task.user_id where create_time=current_date and description="sth" group by user.user_id;

Answer 4

要包含昨天的点数和今天的点数，你可以尝试一下 select user.user_id, count(case when task.create_time=current_date then 1 end) as today_task_count, count(case when task.create_time=DATE_SUB(CURDATE(), INTERVAL 1 DAY) then 1 end) as yesterday_task_count from task left join user on user.user_id=task.user_id where user.description="sth" group by user.user_id;

怎么做WHERE子句BEFORE JOIN

4 个答案: