How to execute PHP query statement by clicking a button to complete data query

In the process of web development, it is often necessary to obtain data from the database. So how to query data from the database through PHP? This article will focus on how to execute PHP query statements by clicking buttons to complete data queries.

1. Create a database and data table

First, we need to create a database and data table in the MySQL database to store data. The test database and test_table data table can be created through the following SQL statements:

CREATE DATABASE test;
USE test;
CREATE TABLE test_table (
    id INT(6) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(30) NOT NULL,
    age INT(6) NOT NULL,
    address VARCHAR(50)
)

2. Connect to the database

In PHP, we can connect to the MySQL database through the mysqli extension. The following is a sample code for connecting to the database:

<?php $servername = "localhost";
$username = "username";
$password = "password";
$dbname = "test";

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

// 检查连接
if (!$conn) {
    die("Connection failed: " . mysqli_connect_error());
}
echo "Connected successfully";
?>

3. Write query statements

Next, we need to write query statements to obtain data. The following is a sample code to obtain all the data in the test_table table:

<?php $sql = "SELECT * FROM test_table";
$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
    // 输出数据
    while($row = mysqli_fetch_assoc($result)) {
        echo "id: " . $row["id"]. " - Name: " . $row["name"]. " - Age: " . $row["age"]. " - Address: " . $row["address"]. "<br>";
    }
} else {
    echo "0 结果";
}
mysqli_close($conn);
?>

4. Click the button to execute the query statement

Through the above code, we can obtain data from the database, but only through The browser automatically executes the query statement when accessing the page. So how to execute the query statement by clicking the button? This can be achieved through the following steps:

1. Add a button in the HTML page

<button>查询</button>

2. Use JavaScript to listen to the click event of the button and send it to the server through Ajax Request

<script>
    $(document).ready(function(){
        $("#query_button").click(function(){
            $.ajax({
                url:"query.php", //请求的PHP文件
                success:function(result){
                    $("#result").html(result); //将结果输出到页面的result标签中
                }
            });
        });
    });
</script>

3. Write the code to execute the query statement in the query.php file and return the result to the client

<?php $sql = "SELECT * FROM test_table";
$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
    // 输出数据
    while($row = mysqli_fetch_assoc($result)) {
        echo "id: " . $row["id"]. " - Name: " . $row["name"]. " - Age: " . $row["age"]. " - Address: " . $row["address"]. "<br>";
    }
} else {
    echo "0 结果";
}
mysqli_close($conn);
?>

Go through the above steps. Implement the function of clicking a button to execute a PHP query statement.

5. Summary

This article introduces how to query data from the database through PHP and execute the query statement by clicking a button. By studying this article, readers can learn how to use the mysqli extension to connect to the MySQL database, how to write query statements, and how to use Ajax to update page content without refreshing the page. Hope this article can be helpful to readers.

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