MySQL 根据 unix 纪元时间戳删除记录

Question

I have a MySQL table as follows:

+----------+---------------------+-----------------+---------------+
| id       | firstName           | lastName        | tstamp        |
+----------+---------------------+-----------------+---------------+
| 133      | James               | Mosher          | 1593612000000 |  
| 145      | Bill                | Turner          | 1593698400000 | 
| 146      | Jeremy              | Vine            | 1593784800000 |  
| 152      | Ramon               | Jesus           | 1593180000000 |
+----------+---------------------+-----------------+---------------+

and I wanted to be able to DELETE records based on the tstamp value (which is epoch unix time) IF they are OLDER than x days . I am using the query below which should only DELETE the last row (Ramon Jesus) as it is older than 5 days ... however, it deletes ALL of the records. Any idea what I am doing wrong?

DELETE FROM students WHERE tstamp > UNIX_TIMESTAMP(DATE_SUB(NOW(), INTERVAL 5 DAY));

Answer 1

Your timestamps contain milliseconds which you must remove prior to the comparison, because UNIX_TIMESTAMP() returns a DATETIME value without milliseconds.
Also the comparison must use the opposite inequality operator:

DELETE FROM students 
WHERE tstamp / 1000 < UNIX_TIMESTAMP(DATE_SUB(NOW(), INTERVAL 5 DAY));

See the demo .
Results:

| id  | firstName | lastName | tstamp        |
| --- | --------- | -------- | ------------- |
| 133 | James     | Mosher   | 1593612000000 |
| 145 | Bill      | Turner   | 1593698400000 |
| 146 | Jeremy    | Vine     | 1593784800000 |