Data merging and splitting technology in PHP database connection

Data merging and splitting technology in PHP database connection

In web application development, database connection is a very important part. As a very commonly used server-side scripting language, PHP provides a wealth of database connection extensions. This article will explore how to use PHP to connect to a database and introduce data merging and splitting techniques.

1. Connect to database

In PHP, by using some specific database connection extensions, we can easily connect to various types of databases, including MySQL, Oracle, SQLite wait. Here we take MySQL as an example.

First, we need to introduce the MySQL extension into the PHP code. This extension can be enabled through the extension= item in the php.ini file. Then, we need to use the mysqli_connect() function to establish a connection to the database. The following is a simple example:

<?php
$host = 'localhost';
$username = 'root';
$password = 'password';
$database = 'mydb';

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

if (!$conn) {
    die('数据库连接失败: ' . mysqli_connect_error());
}

echo '数据库连接成功';
?>

By calling the mysqli_connect() function, we pass in the required host address, user name, password and database name, and return a connection object $conn . If the connection is successful, "Database connection successful" is output; otherwise, the corresponding error message is output.

2. Data Merging

In some cases, we need to get data from multiple database tables and merge them into a result set. In PHP, we can achieve this using union queries of SQL statements. The following is a simple example:

<?php
$sql1 = 'SELECT * FROM table1';
$sql2 = 'SELECT * FROM table2';
$sql = $sql1 . ' UNION ' . $sql2;

$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
    while ($row = mysqli_fetch_assoc($result)) {
        // 处理数据
    }
} else {
    echo '未找到数据';
}

mysqli_free_result($result);
mysqli_close($conn);
?>

In the above example, we defined two SQL statements $sql1 and $sql2, and then spliced ​​the two statement to get a new SQL statement $sql, which uses the UNION keyword to merge the result set. Finally, we execute the SQL statement by calling the mysqli_query() function, and use the mysqli_num_rows() function to determine whether the data is found. If the data is found, the data is fetched row by row through the mysqli_fetch_assoc() function.

3. Data splitting

Sometimes, we need to split a large data set into multiple smaller subsets. In PHP, you can use LIMIT and OFFSET to achieve data splitting. Here is an example:

<?php
$limit = 10; // 每页显示的记录数
$page = isset($_GET['page']) ? $_GET['page'] : 1; // 当前页码

$offset = ($page - 1) * $limit;
$sql = 'SELECT * FROM table LIMIT ' . $offset . ',' . $limit;

$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
    while ($row = mysqli_fetch_assoc($result)) {
        // 处理数据
    }
} else {
    echo '未找到数据';
}

mysqli_free_result($result);
mysqli_close($conn);
?>

In the above example, we first define the number of records displayed per page $limit and the current page number $page. Then, by calculating the offset $offset, the displayed data range is determined based on the relationship between the current page number and the number of records per page. Finally, use LIMIT and OFFSET to limit the scope of the query results.

Summary

Through the introduction of this article, we have learned how to use PHP to connect to the database, and learned the technology of data merging and splitting. These technologies are very common in actual web application development and play an important role in improving efficiency and performance. I hope this article is helpful to you, thank you for reading!

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