How to use PHP to perform database search and modification operations

In web development, the database is an integral part. PHP, as a popular web programming language, integrates very well with various database systems. In PHP, MySQL is one of the most commonly used relational database systems.

In PHP, database operations are usually divided into two categories: search and modification. The search operation refers to obtaining data from the database and displaying it, while the modification operation refers to adding, deleting, modifying and other operations to the data in the database. This article will introduce how to use PHP to perform database search and modification operations.

1. Database connection

Before performing database operations, we need to connect to the database first. In PHP, you can use mysqli and PDO to implement database connections and operations. This article introduces the mysqli connection method.

To connect to the MySQL database, we need to define the host name, user name and password required to access the database, as well as the name of the database to be accessed. The following is a sample code for connecting to a MySQL database:

$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// 创建连接
$conn = new mysqli($servername, $username, $password, $dbname);

// 检查连接是否成功
if ($conn->connect_error) {
    die("连接失败: " . $conn->connect_error);
}
echo "连接成功";

2. Database search operation

The common ways to perform database search operations are as follows:

1. Use the SELECT statement to query data

The SELECT statement is the most commonly used query statement. It can get data from one or more tables and filter based on conditions. The following is a sample code for using the SELECT statement to query data:

$sql = "SELECT id, name, email FROM users";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // 输出数据
    while($row = $result->fetch_assoc()) {
        echo "id: " . $row["id"]. " - Name: " . $row["name"]. " - Email: " . $row["email"]. "<br>";
    }
} else {
    echo "0 结果";
}

2. Querying data using the WHERE clause

The WHERE clause is used to filter data that meets specified conditions. The following is a sample code for querying data using the WHERE clause:

$sql = "SELECT id, name, email FROM users WHERE name='John'";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // 输出数据
    while($row = $result->fetch_assoc()) {
        echo "id: " . $row["id"]. " - Name: " . $row["name"]. " - Email: " . $row["email"]. "<br>";
    }
} else {
    echo "0 结果";
}

3. Querying data using LIKE

The LIKE operator is used for fuzzy matching in the WHERE clause. The following is a sample code for using LIKE to query data:

$sql = "SELECT id, name, email FROM users WHERE name LIKE '%John%'";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // 输出数据
    while($row = $result->fetch_assoc()) {
        echo "id: " . $row["id"]. " - Name: " . $row["name"]. " - Email: " . $row["email"]. "<br>";
    }
} else {
    echo "0 结果";
}

3. Database modification operations

The common ways to perform database modification operations are as follows:

1. Insert data using the INSERT statement

The INSERT statement is used to insert data into the database. The following is a sample code to insert data using the INSERT statement:

$sql = "INSERT INTO users (name, email, password)
VALUES ('John', 'john@example.com', '12345')";
if ($conn->query($sql) === TRUE) {
    echo "新纪录插入成功";
} else {
    echo "Error: " . $sql . "<br>" . $conn->error;
}

2. Update data using the UPDATE statement

The UPDATE statement is used to update data in the database. The following is a sample code for updating data using UPDATE statement:

$sql = "UPDATE users SET email='john@example.com' WHERE name='John'";
if ($conn->query($sql) === TRUE) {
    echo "数据更新成功";
} else {
    echo "Error updating record: " . $conn->error;
}

3. Deleting data using DELETE statement

DELETE statement is used to delete data from the database. The following is a sample code for using the DELETE statement to delete data:

$sql = "DELETE FROM users WHERE name='John'";
if ($conn->query($sql) === TRUE) {
    echo "数据删除成功";
} else {
    echo "Error deleting record: " . $conn->error;
}

IV. Summary

This article introduces common ways to use PHP to perform database search and modification operations, including using SELECT statement to query data, use WHERE clause to query data, use LIKE to query data, use INSERT statement to insert data, use UPDATE statement to update data and use DELETE statement to delete data. Mastering these skills will make you better at web development using PHP and MySQL.

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