如何选择最后一天插入的所有行？

Question

I have a table like this:

// reset_password_emails
+----+----------+--------------------+-------------+
| id | id_user  |        token       | unix_time   |
+----+----------+--------------------+-------------+
| 1  | 2353     | 0c274nhdc62b9dc... | 1339412843  |
| 2  | 2353     | 0934jkf34098joi... | 1339412864  |
| 3  | 5462     | 3408ujf34o9gfvr... | 1339412894  |
| 4  | 3422     | 2309jrgv0435gff... | 1339412899  |
| 5  | 3422     | 34oihfc3lpot4gv... | 1339412906  |
| 6  | 2353     | 3498hfjp34gv4r3... | 1339412906  |
| 16 | 2353     | asdf3rf3409kv39... | 1466272801  |
| 7  | 7785     | 123dcoj34f43kie... | 1339412951  |
| 9  | 5462     | 3fcewloui493e4r... | 1339413621  |
| 13 | 8007     | 56gvb45cf3454g3... | 1339424860  |
| 14 | 7785     | vg4er5y2f4f45v4... | 1339424822  |
+----+----------+--------------------+-------------+

Each row is an email. Now I'm trying to implement a limitation for sending-reset-password email. I mean an user can achieve 3 emails per day (not more) .

So I need an query to check user's history for the number of emails:

SELECT count(1) FROM reset_password_emails WHERE token = :token AND {from not until last day}

How can I implement this:

. . . {from now until last day}

---

Actually I can do that like: NOW() <= (unix_time + 86400) .. But I guess there is a better approach by using interval . Can anybody tell me what's that?

Answer 1

Your expression will work, but has 3 problems:

1. the way you've coded it means the subtraction must be performed for every row (performance hit)
2. because you're not using the raw column value, you couldn't use an index on the time column (if one existed)
3. it isn't clear to read

Try this:

unix_time > unix_timestamp(subdate(now(), interval '1' day))

here the threshold datetime is calculated once per query, so all of the problems above have been addressed.

See SQLFiddle demo

Answer 2

You can convert your unix_time using from_unixtime function

select r.*
  from reset_password_emails r
 where now() <= from_unixtime(r.unix_time) - interval '1' day

Just add the extra filters you want.

See it here: http://sqlfiddle.com/#!9/4a7a9/3

It evaluates to no rows because your given data for unix_time field is all from 2011

Edited with a sqlfiddle that show the conversion:

http://sqlfiddle.com/#!9/4a7a9/4