How to delete and modify data in database in php? (code example)

PHP is a popular server-side scripting language commonly used for web development and the creation of dynamic web pages. PHP can use many different methods when working with a database, including code that deletes and modifies the database. In this article, I will explain how to write code to delete and modify a database using PHP.

1. Deleting data in the database

Deleting data in the database is a common requirement. Deleting data from a database usually requires the use of SQL statements. The following is a sample code:

<?php     //连接数据库
    $conn = mysqli_connect("localhost", "username", "password", "dbname");
  
    //检查连接
    if (!$conn) {
        die("Connection failed: " . mysqli_connect_error());
    }
  
    //定义SQL语句
    $sql = "DELETE FROM tablename WHERE id=1";
  
    //执行SQL语句
    if (mysqli_query($conn, $sql)) {
        echo "Record deleted successfully";
    } else {
        echo "Error deleting record: " . mysqli_error($conn);
    }
  
    //关闭连接
    mysqli_close($conn);
?>

The above sample code executes a DELETE statement to delete the record with id 1 from the table named "tablename". In practical applications, SQL statements can be modified according to actual needs.

2. Modify the data in the database

Modifying the data in the database is also a common requirement. Modifying data also requires the use of SQL statements. The following is a sample code:

<?php     //连接数据库
    $conn = mysqli_connect("localhost", "username", "password", "dbname");
  
    //检查连接
    if (!$conn) {
        die("Connection failed: " . mysqli_connect_error());
    }
  
    //定义SQL语句
    $sql = "UPDATE tablename SET firstname=&#39;John&#39;, lastname=&#39;Doe&#39; WHERE id=1";
  
    //执行SQL语句
    if (mysqli_query($conn, $sql)) {
        echo "Record updated successfully";
    } else {
        echo "Error updating record: " . mysqli_error($conn);
    }
  
    //关闭连接
    mysqli_close($conn);
?>

The above sample code executes an UPDATE statement to update the firstname and lastname of the record with id 1 from the table named "tablename" field. In actual applications, SQL statements can also be modified according to actual needs.

Summary

PHP can use many different methods to delete or modify data in the database. SQL statements are typically used to accomplish these tasks. When writing and executing SQL statements, you need to pay attention to security issues, such as SQL injection attacks. By understanding and learning how PHP interacts with databases, developers can process data in databases more efficiently and build more reliable and secure web applications.

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