如何使用变量更新mysql数据库？

Question

To all experts who is going to read this question, It is a basic problem that cost me more than hours to me,

I want to update previously entered row. As it can be seen in the code, I want to update Improvement column. Also I want to do that with the help of the last user id, which is a auto increment primary key entry. However with the code I wrote down here nothing changes in my Mysql database.

$sql = "
UPDATE users 
SET Improvement='".$improvement."'
WHERE ORDER BY User_id DESC LIMIT 1 
";  

mysql_query($sql, $accounts);

And as you can see this is my table in mysql,

users   CREATE TABLE `users` (
 `Username` varchar(30) COLLATE latin1_general_ci NOT NULL,
 `Age` varchar(20) COLLATE latin1_general_ci NOT NULL,
 `Education` varchar(20) COLLATE latin1_general_ci NOT NULL,
 `Department` varchar(20) COLLATE latin1_general_ci NOT NULL,
 `Favourite` varchar(20) COLLATE latin1_general_ci NOT NULL,
 `Preference` varchar(20) COLLATE latin1_general_ci NOT NULL,
 `Lpreference` varchar(20) COLLATE latin1_general_ci NOT NULL,
 `Level` varchar(20) COLLATE latin1_general_ci NOT NULL,
 `Question` varchar(20) COLLATE latin1_general_ci NOT NULL,
 `Improvement` int(11) NOT NULL,
 `User_id` int(11) NOT NULL AUTO_INCREMENT,
 PRIMARY KEY (`User_id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_general_ci

I believe I cannot update Improvement column because of the syntax. In my page no error occurs, and nothing happens even though $improvement not equal to 0. I echo the $improvement variable it is not equal to 0. But noting changes in my database.

I am desperate for an answer, If it works I will select it as best answer for other people who is facing the same problem.

Answer 1

Try with -

$sql = "UPDATE users SET Improvement='".$improvement."' ORDER BY User_id DESC LIMIT 1";  

mysql_query($sql, $accounts);