Increase and decrease row value by 1 in MySQL - php

Question

Hi I have a MySQL database table "points" the user can click a button and a point should be removed from their account, the button they pressed has an ID of another user, therefore their account must increase by one.
I have it working in jQuery and checked the varibles/posts in Firebug, and it does send the correct data, such as:
userid= 1
posterid = 4
I think the problem is with my PHP page:
<?php
include ('../functions.php');
$userid=mysql_real_escape_string($_POST['user_id']);
$posterid=mysql_real_escape_string($_POST['poster_id']);
if (loggedin())
{
include ('../connection.php');
$query1 = "UPDATE `points` SET `points` = `points` - 1 WHERE `userID` = '$userid'";
$result1=mysql_query($query1);
$query2 = "UPDATE `points` SET `points` = `points` + 1 WHERE `userID` = '$posterid'";
$result2=mysql_query($query2);
if ($result1 && result2)
{
echo "Successful";
return 1;
}
else
{
echo mysql_error();
return 0;
}
}
?>
Any ideas? Thanks :)

Answer 1

Two queries to increase/decrease field value are not necessary:
UPDATE table SET field = field + 1 WHERE id = 1
is a perfectly valid query as you can see next:
mysql> describe points;
+--------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------+---------+------+-----+---------+-------+
| uid | int(11) | NO | PRI | NULL | |
| points | int(11) | YES | | 0 | |
+--------+---------+------+-----+---------+-------+
2 rows in set (0.05 sec)
mysql> insert into points VALUES (1,0),(2,0);
Query OK, 2 rows affected (0.14 sec)
mysql> select * from points;
+-----+--------+
| uid | points |
+-----+--------+
| 1 | 0 |
| 2 | 0 |
+-----+--------+
2 rows in set (0.05 sec)
mysql> update points set points = points+1 where uid = 1;
Query OK, 1 row affected (0.27 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from points;
+-----+--------+
| uid | points |
+-----+--------+
| 1 | 1 |
| 2 | 0 |
+-----+--------+
2 rows in set (0.00 sec)
Having that tested, are you sure you get into your if (loggedin()) clause?
I have to agree with KM, would be nice to see output of echo $query1; or echo $query2;

Answer 2

Here is the example query, tested by me and it is working 100%
$query="UPDATE table_name SET `hit_count`=(`hit_count`+1) WHERE `id` = '1'";

Answer 3

update table_name set col_name=col_name+1 where sqId = 12
But if your col_name by default value is null or empty it never works, so make sure that col_name default value is 0 or any integer value.

Answer 4

update 'tablename' set 'columnname1'='columnname1' + 1 where 'columnname2'='value';
eg: update students set englishmarks=englishmarks + 1 where name='Rahul';
Edit:(Explanation)
"UPDATE" keyword is used to update a vaule in the table. Here I am updating a value in the table "students". "SET" keyword updating the english marks by 1(just like in C language, how we increase the value of an integer, i=i+1) and condidtion is given where name is "Rahul".
So englishmarks of Rahul are incremented by 1

Answer 5

In laravel Migration do:
\DB::statement('SELECT #pos:=0;');
\DB::statement('UPDATE users SET company_id = ( SELECT #pos := #pos + 1 ) WHERE `id` = '1';');
If want to change all records, remove the WHERE id = '1'
It will insert number increment to your records like:
+-----+------------+
| id | company_id |
+-----+------------+
| 1 | 1 |
| 12 | 2 |
| 23 | 3 |
+-----+------------+