使用PHP从MYSQL中检索记录并比较日期时间数据[重复]

This question already has an answer here:

my MYSQL table is as below:

id   record_nr    timestamp
1    931          2014-02-15 6:21:00
2    577          2013-05-03 0:19:00
3    323          2012-08-07 11:26:00

in PHP I tried to retrieve a record by comparing time as below:

$dateTimeString = "2013-07-28 7:23:34";

$query = "SELECT * FROM mytable ";
$query .= "WHERE timestamp <= STR_TO_DATE('".$dateTimeString."', '%H:%i:%s')";
$query .= " ORDER BY timestamp DESC LIMIT 1";

This didn't work. How to retrieve the record #577? Timestamp is not the time the record was created. Rather, it is a date and time associated with that record.

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Below code can be helpful:

$dateTimeString = '2016-12-27 12:59:46';
$query = "SELECT * FROM `mytable` 
WHERE `TIMESTAMP` <= '".$dateTimeString."' 
ORDER BY TIMESTAMP DESC LIMIT 1";

I changed to

$query .= "WHERE timestamp <= '".$dateTimeString."'";

It seems to work. Thanks.