Analyze and solve the problem of php mysql statement not executing

During the development of php/mysql, we often encounter the problem of statements not being executed. This is a very common problem. In this article, we will discuss the possible causes of this problem and provide solutions.

1. Check the connection
   Before using the mysql statement, you must ensure that the connection has been established. If the connection is not established, the mysql statement will not be executed. You can use the following code to test whether the connection is established:

$conn = mysqli_connect($server, $username, $password, $database);

if(!$conn) {
    echo "无法连接到数据库，请检查用户名和密码";
}

2. Check syntax
   Make sure the syntax of your mysql statement is correct. If the syntax is incorrect, the mysql statement will be ignored and not will be executed. You can use the following code to check for syntax errors:

$result = mysqli_query($conn, $sql);

if(!$result) {
    echo "查询语句有误: " . mysqli_error($conn);
}

3. Check permissions
   Make sure your mysql user has the permission to execute the relevant mysql statement. If your mysql user does not have the permission, mysql The statement will be ignored and not executed. You can use the following code to test whether the mysql user has the relevant permissions:

$conn = mysqli_connect($server, $username, $password, $database);

if(!$conn) {
    echo "无法连接到数据库，请检查用户名和密码";
}

// 用户权限测试
$sql = "SELECT * FROM `table`";
$result = mysqli_query($conn, $sql);
if(!$result) {
    echo "您的用户没有执行该操作的权限";
}

4. Check variables
   Make sure your variables are initialized correctly. If the variables fail to be successfully initialized, the mysql statement will not be executed. You can use the following code to check whether the variables are initialized correctly:

$variable = "";

if(empty($variable)) {
    echo "变量未被正确初始化";
}

5. Check the database status
   If your database status is incorrect, the mysql statement will not be executed. You can use the following code to check whether the database status is correct:

$conn = mysqli_connect($server, $username, $password, $database);

if(mysqli_connect_errno()) {
    echo "无法连接到数据库: " . mysqli_connect_error();
}

// 检查数据库的状态
if(mysqli_ping($conn)) {
    echo "数据库连接正常";
} else {
    echo "数据库连接出现问题";
}

Summary
When doing php/mysql development, statement not executing is a very common problem. The solutions provided above are universal and can help you solve the problem quickly. However, sometimes these solutions don't completely solve the problem and more in-depth investigation may be required. When the problem cannot be solved, please be sure to consult the official documentation to find a better solution.

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