Mysql：选择具有两个条件的不同值

Question

I have a table called jobs with fields: id, status. And another table called jobs_history with fields: id, jobid, status, added_time.

Every time a job is edited through php, I insert the updated data into jobs_history table with jobid, user selected status, and added_time.

A job maybe edited many times so there could be many rows in jobs_history table for one job. And the status field may contains different status like, 1st status would be "Under review", 2nd could be "In progress", 3rd could be "E-mail sent", 4th "Completed".

Now, I need to count the total number of jobs at a specific datetime that had status "In progress" on that date. Here is some example data in jobs_history table:

id | jobid | status       | added_time
--------------------------------------
1  | 10    | Under review | 2014-05-20 01:00:00
2  | 10    | In progress  | 2014-05-21 02:30:00
3  | 10    | E-mail sent  | 2014-05-23 10:00:00
4  | 10    | Completed    | 2014-05-23 04:00:00
5  | 11    | Under review | 2014-05-19 05:00:00
6  | 11    | In progress  | 2014-05-20 06:00:00
7  | 11    | E-mail sent  | 2014-05-20 07:00:00
8  | 11    | Completed    | 2014-05-22 08:00:00
9  | 12    | Under review | 2014-05-23 09:00:00
10 | 12    | In progress  | 2014-05-24 02:00:00
11 | 13    | Under review | 2014-05-20 10:00:00
12 | 13    | In progress  | 2014-05-20 12:00:00

I want to count total number of jobs that had status "In progress" on the 2014-05-21 06:00:00. The query should produce result 2, that is jobid 10 and 13, because those are the only jobs that had last status "In progress" on 2014-05-21 06:00:00.

I have about 400,000 data in the jobs_history table so the query should be written in the fastest way possible.

Thanks and I very much appreciate your help on this.

Answer 1

If your date format is different you can use date_format function. Check this link http://sqlfiddle.com/#!2/4a6e8b/17