Increment value in MySQL update query

Question

I have made this code for giving out +1 point, but it doesn't work properly.

mysql_query("
    UPDATE member_profile 
    SET points= ' ".$points." ' + 1 
    WHERE user_id = '".$userid."'
");

The $points variable is the user's points right now. I want it to add one to it. So example if he had like 5 points, it should be 5+1 = 6, but it doesn't, it just changes to 1.

What have I done wrong?

Answer 1

Simply increment the value that already exists in the database

$sql = "UPDATE member_profile SET points = points + 1 WHERE user_id = ?";
$db->prepare($sql)->execute([$userid]);

This code would work for both PDO and mysqli in the modern PHP versions

Answer 2

您可以执行此操作而无需查询实际的点数，因此它会在脚本执行期间为您节省一些时间和资源。

mysql_query("UPDATE `member_profile` SET `points`= `points` + 1 WHERE `user_id` = '".intval($userid)."'");

Answer 3

"UPDATE member_profile SET points = points + 1 WHERE user_id = '".intval($userid)."'"

Answer 4

Hope I'm not going offtopic on my first post, but I'd like to expand a little on the casting of integer to string as some respondents appear to have it wrong.

Because the expression in this query uses an arithmetic operator (the plus symbol +), MySQL will convert any strings in the expression to numbers.

To demonstrate, the following will produce the result 6:

SELECT ' 05.05 '+'.95';

String concatenation in MySQL requires the CONCAT() function so there is no ambiguity here and MySQL converts the strings to floats and adds them together.

I actually think the reason the initial query wasn't working is most likely because the $points variable was not in fact set to the user's current points. It was either set to zero, or was unset: MySQL will cast an empty string to zero. For illustration, the following will return 0:

SELECT ABS('');

Like I said, I hope I'm not being too off-topic. I agree that Daan and Tomas have the best solutions for this particular problem.

Answer 5

此外，要“增加”字符串，更新时，使用CONCAT

update dbo.test set foo=CONCAT(foo, 'bar') where 1=1

Answer 6

Who needs to update string and numbers

SET @a = 0;
UPDATE obj_disposition SET CODE = CONCAT('CD_', @a:=@a+1);

Answer 7

The accepted answer is good but not working with null values try this

mysql_query("
    UPDATE member_profile 
    SET points = IFNULL(points, 0) + 1
    WHERE user_id = '".$userid."'
");

More info on IFNULL

Answer 8

You should use PDO to prevent SQL injection risk.

You can connect to DB like this :

$pdo_options[PDO::ATTR_ERRMODE] = PDO::ERRMODE_EXCEPTION;
$bdd = new PDO('mysql:host=xxxx;dbname=xxxx;charset=utf8mb4', 'user', 'password', $pdo_options);

No need to query DB to get the number of points. You can increment directly in the update query ( points = points + 1 ).

(note : Also, it's not a good idea to increment the value with PHP because you need to select first the data and the value can changed if other users are updated it.)

$req = $bdd->prepare('UPDATE member_profile SET 
            points = points + 1
            WHERE user_id = :user_id');

$req->execute(array(
    'user_id' => $userid
));

Answer 9

Remove the ' around the point :

mysql_query("UPDATE member_profile SET points=".$points."+1 WHERE user_id = '".$userid."'");

You are "casting" an integer value to string in your original query...

Answer 10

为什么不让 PHP 完成这项工作？

"UPDATE member_profile SET points= ' ". ($points+1) ." '  WHERE user_id = '".$userid."'"