PHP SQL AJAX get data from before certain datetime - php

Question

I am comparing two datetime in the SQL statement. This is done in PHP.
$result=mysqli_query($con,"SELECT
*
FROM
join
WHERE
join_date <= '$last_join_dates'
ORDER BY
join_date DESC LIMIT 3 OFFSET 3");
$last_join_dates gets update every time, so that I use offset to keep pulling in new data. However, comparing the date is not actually working.
Inside database: structure join_date looks like 2015-10-24 13:30:22 and it is a datetime type.
$last_join_datesI use is the exact same format 2015-10-26 08:23:22.
Since that doesn't work.. I tried the following to convert them.
TRIED FORMAT() the datetime, but does not work:
$result=mysqli_query($con,"SELECT
*
FROM
join
WHERE
FORMAT(join_date, 'yyyyMMddhhmmss') <= FORMAT($last_join_dates, 'yyyyMMddhhmmss')
ORDER BY
join_date DESC LIMIT 3 OFFSET 3");
TRIED Convert() the datetime, but doesn't seem to work either:
$result=mysqli_query($con,"SELECT
*
FROM
join
WHERE
REPLACE(REPLACE(REPLACE(CONVERT(VARCHAR(19), CONVERT(DATETIME, join_date, 112), 126), '-', ''), 'T', ''), ':', '') <= REPLACE(REPLACE(REPLACE(CONVERT(VARCHAR(19), CONVERT(DATETIME, $last_join_dates, 112), 126), '-', ''), 'T', ''), ':', '')
ORDER BY
join_date DESC LIMIT 3 OFFSET 3");
I'm not sure how to debug this.. Any suggestions?

Answer 1

well #1, JOIN is a mysql keyword so you need to either put back-ticks around it or better yet call your table something else
#2, this wouldn't be the reason it isn't working, but you should never use string interpolation like that, it is vulnerable to sql injection. Instead use $last_join_date as a bind variable: Bind variables in a mysql_query statement
The SQL you have above is correct, as seen below:
mysql> select * from test order by the_date;
+----+---------------------+
| id | the_date |
+----+---------------------+
| 1 | 2015-01-02 11:23:21 |
| 2 | 2015-01-03 12:23:21 |
| 3 | 2015-02-03 12:25:21 |
| 4 | 2015-02-05 12:25:21 |
| 5 | 2015-02-05 15:25:21 |
| 6 | 2015-02-05 15:37:21 |
| 7 | 2015-02-05 20:37:21 |
| 8 | 2015-02-05 20:37:40 |
| 9 | 2015-03-05 20:37:40 |
| 10 | 2015-03-06 20:37:40 |
+----+---------------------+
10 rows in set (0.00 sec)
mysql> select * from test where the_date <= '2015-02-10 01:12:24' order by the_date desc limit 3, 3;
+----+---------------------+
| id | the_date |
+----+---------------------+
| 5 | 2015-02-05 15:25:21 |
| 4 | 2015-02-05 12:25:21 |
| 3 | 2015-02-03 12:25:21 |
+----+---------------------+
3 rows in set (0.00 sec)
So try naming the table something else or use backticks "`". Also try running the query from the mysql command line. Maybe the data you have isn't what you thought but the query is working fine.

Answer 2

Try this one:
"SELECT * FROM join WHERE join_date <= '".date("Y-m-d H:i:s", strtotime($last_join_dates))."'ORDER BY join_date DESC LIMIT 3 OFFSET 3"
It converts $last_join_dates to a timestamp using strtotime, then the date function will convert it to the proper format.

Answer 3

Try this:
$result=mysqli_query($con,"SELECT
*
FROM
join
WHERE
UNIX_TIMESTAMP(join_date) <= '" . strtotime($last_join_dates) . "'
ORDER BY
join_date DESC LIMIT 3 OFFSET 3");