I have MySQL table:
and I want to add next row (from script in page) with values:
ip: 178.40.12.36
time: 2014-01-22 14:08:04
browser: Google Chrome
browser_version: 32.0.1700.76
platform: windows
country: Slovakia
Question: How to determine in mysql query to insert only if last insert with same identificator (IP+browser+platform) was 30min ago ?
My current insert (pseudo code):
$exist = SELECT *
FROM table
WHERE ip = $ip
AND browser = $browser
AND platform = $platform
if(!$exist) {
INSERT INTO table ...
}
My Idea:
$exist = SELECT ...
...
AND time < $time - 30MIN
Note: How to write this in MySQL?
You may use this as indicator:
SELECT
COUNT(1)
FROM `t`
WHERE `ip` = '$ip'
AND `browser` = '$browser'
AND `platform` = '$platform'
AND `time`>NOW() - INTERVAL 30 MINUTE
-I've replaced time with NOW() for current time, but you may wish to count from your last time value.
It will select records what are newer than 30 minutes, thus, if it's positive, then you don't need to insert new row(s).
Yes, it's easy.
AND time > NOW() - INTERVAL 30 MINUTE
There are many choices like this for date arithmetic.
You could just filter the SELECT for the INSERT:
INSERT INTO `Table` ( ... )
SELECT $ip, $time, $browser, $browser_version, $platform, $country
FROM `Other_Table`
WHERE ip = $ip AND browser = $browser AND platform = $platform AND
time < $time - 30MIN
Now, clearly that syntax won't work exactly, but you get the idea. If the time isn't 30MIN or more ago then it will return 0 records to INSERT.
This will avoid the need of performing a COUNT or EXISTS first; it can be done in one statement.
Related
I have around 500,000 records of personal profile in MySQL database containing a birthdate column (dob). Since I had to get the ages for each profile, I needed to calculate it dynamically which I can either do via PHP (date_diff(date_create($dob), date_create('today'))->y) or through SQL ('SELECT TIMESTAMPDIFF(YEAR, dob, CURDATE()) AS age').
Which of the two is faster or more preferred especially if I have hundreds of thousands of rows?
In general, the best approach is to do such calculations on the server.
The ideal approach would be to use a generated column. This has been available since MySQL 5.7.5, and would be expressed as:
alter table t add age unsigned as
(TIMESTAMPDIFF(YEAR, dob, CURDATE()));
Alas, you can only use deterministic functions for generated columns. curdate() and now() are not deterministic, because their values can change with each call.
The next best thing is to use a view:
create view v_t as
select t.*,
TIMESTAMPDIFF(YEAR, dob, CURDATE())
from t;
Then, when you query the view, you'll have the age. This is true no matter where you query it. And it is the same logic everywhere.
The only caveat to doing the calculation on the server is that it uses server time, rather than local application time. If that is an issue, then that is a strong argument for doing the calculation locally.
Here is a test:
Create a table with 100K random dates
drop table if exists birthdays;
create table birthdays (
id int auto_increment primary key,
dob date
);
insert into birthdays (dob)
select '1950-01-01' + interval floor(rand(1)*68*365) day as dob
from information_schema.COLUMNS c1
, information_schema.COLUMNS c2
, information_schema.COLUMNS c3
limit 100000
;
Run this PHP script
<?php
header('Content-type: text/plain');
$db = new PDO("mysql:host=localhost;dbname=test", "test","");
### SQL
$starttime = microtime(true);
$stmt = $db->query("SELECT id, dob, TIMESTAMPDIFF(YEAR, dob, CURDATE()) AS age FROM birthdays");
$data = $stmt->fetchAll(PDO::FETCH_OBJ);
$runtime = microtime(true) - $starttime;
echo "SQL: $runtime \n";
### PHP
$starttime = microtime(true);
$stmt = $db->query("SELECT id, dob FROM birthdays");
$data = $stmt->fetchAll(PDO::FETCH_OBJ);
foreach ($data as $row) {
$row->age = date_diff(date_create($row->dob), date_create('today'))->y;
}
$runtime = microtime(true) - $starttime;
echo "PHP: $runtime \n";
Result:
SQL: 0.19094109535217
PHP: 1.203684091568
It looks like the SQL solution is 6 times faster. But that is not quite true. If we remove the code which calculates the age from both solutions, we will get something like 0.1653790473938. That means the overhead for SQL is 0.025 sec, while for PHP it is 1.038 sec. So SQL is 40 times faster in this test.
Note: There are faster ways to calculate the age in PHP. For example
$d = date('Y-m-d');
$row->age = substr($d, 0, 4) - substr($row->dob, 0, 4) - (substr($row->dob, 5) > substr($d, 5) ? 1 : 0);
is like four times faster - while date('Y-m-d') consumes more than 80% of the time. If you find a way to avoid any date function, you might get close to the performance of MySQL.
if you want get all 500,000 records you should do this in MySql because performance is better than PHP
but, if you want get some of that data (for example 10 records) , do that with PHP it's better to handle. and performance not different
As the title says.
From the database, in the resultset, I want those rows where the date and time (schedule column) are already passed.
In the database I have
On the PHP page I have:
$now = time();
$result = $mysqli->query("SELECT * FROM schedules WHERE $now >= UNIX_TIMESTAMP(schedule)");
However, if I test this on 2015-09-19 at 18:50:00, I get no results at all, while instead I should only get the row with ID 39.
As much as I know I am comparing two valid timestamps - the one generated by time() and the one converted from the database with UNIX_TIMESTAMP() - so what isn't working?
EDIT: I already tried to do
$result = $mysqli->query("SELECT * FROM schedules WHERE NOW() >= schedule");
But with no luck. I am getting the results with
while ($row = $result->fetch_assoc()) {
$id = $row['ID'];
echo $id;
}
Use now() to select rows where schedule is in the past
SELECT * FROM schedules WHERE now() > schedule
They are different because,
php time is based on the php timezone setting (inside php.ini).
database time is based on your system time (unless you set it).
I am trying to write a PHP script that will count the amount of users that have visited the page within the last 10 minutes. This is my script right now:
function getOnlineUsers($database, $main_connection){
$database;
$visitor_id = session_id();
$timestamp = time();
$timeOut = $timestamp - 6000;
mysql_query("INSERT INTO online (m_time, ip) VALUES ('$timestamp', '$visitor_id')", $main_connection);
mysql_query("DELETE FROM online WHERE m_time < $timeOut");
$result = mysql_query("SELECT * FROM online");
mysql_fetch_assoc($result);
if(!$result){
$online_users = 1;
}else{
$online_users = mysql_num_rows($result);
}
return $online_users+1;
}
The problem is that nothing is being inserted into the database and the database remains empty and therefore the count is null. Can someone please assist me in this?
First, better use PDO or MySQLi. In your database, the 'm_time' column must be integer type, and pass the $timestamp value as number, not within quotes.
"INSERT INTO online (m_time, ip) VALUES ($timestamp, '$visitor_id')"
1) Change '$timestamp' to NOW(), mysql can't understand php's time() function ( assuming m_time is a datetime field) .
ie:
INSERT INTO online (m_time, ip)
VALUES ( NOW(), '$visitor_id')
2) Your delete suffers the same problem
3) You can use something a little more clever to get the users in the last 10 minutes, try something like:
select count(*) AS OnlineUserCount
from online
WHERE
m_time > DATE_SUB( NOW(), INTERVAL 10 MINUTE ) ;
Your code looks fine .. what i suggest you do is echo out the query when it runs and cope and paste it and run it directly from phpmyadmin and check if it gives you any error and if the row is inserted succesfully i suggest you check your connection file with the database.
And also try what's suggested by CoursesWeb
Hello in a PHP Script i have the following MySQL Query
$query_players = "SELECT (current_timestamp -`Online_since`) AS `Since` FROM `streams` WHERE `Team` = $temp AND `Online` = 1 ORDER BY `Viewers` DESC";
then i have:
$since = round($obj_players->Since /3600);
As you probably can imagine $since should contain how long the player is already online in hours. Strangely it has wrong results. Its like the time goes faster in MySQL :P
For example after about 15 minutes it already shows "Online since 1 hour" another approximately 30 mins later it already shows 2 hours and so on.
Anyone know what could be wrong? Maybe current_timestamps is the problem?
current_timestamp is not really measured in seconds. So dividing the difference by 3600 doesn't yield hours, but some arbitrary value.
The difference after 18 minutes is 1800 and round(1800/3600) = round(0.5) gives of course 1.
Depending on your real column type use either timediff() or timestampdiff() for your calculation.
Try using TIMESTAMPDIFF:
$query_players = "SELECT TIMESTAMPDIFF(HOUR, NOW(), `Online_since`) AS `Since`
FROM `streams`
WHERE `Team` = $temp
AND `Online` = 1
ORDER BY `Viewers` DESC";
In my code, I am trying to find items in an activities table that are within the last day. This query is not returning any results, are there any problems with it? Is there a better query?
$curday = time() - (24*3600);
$query = "SELECT * FROM activities WHERE userid = '$userid' AND 'timestamp' > '$curday'";
There are two choices here, you can get and format the date through PHP or use SQL language to do it. I prefer to do it within the SQL, it also allows me to use the same query in a MySQL client.
This question is essentially the same thing: MySQL SELECT last few days?
This would be the new query:
$query = "SELECT * FROM activities WHERE userid = '$userid' AND 'timestamp' > DATE_ADD(CURDATE(), INTERVAL -1 DAY)";
you can try with unix function 'mktime' to get value of yesterday ..
as
$curday = mktime(0,0,0,date("m"),date("d")-1,date("Y"));
for reference
if your database will mysql only then you can extract yesterday in sql itself..
SELECT * FROM activities
WHERE userid = '$userid'
AND timestamp > DATE_SUB(CONCAT(CURDATE(), ' 00:00:00'), INTERVAL 1 DAY)
one more thing if timestamp is your column name don't put this column inside single quote ..
What you can use is DATE_SUB. This can be used as follows
SELECT * FROM activities
WHERE userid = '$userid'
AND timestamp > date_sub(current_date, interval 1 day)
This way you don't need to work with current date in PHP
in Informix it would be (TODAY - 1) if the column is type DATE