Plugin database tables in Wordpress - Mini Project: Build & Apply

Create and Use Plugin Database Tables in WordPress

📖 Scenario: You are building a WordPress plugin that needs to store custom data in its own database table. This is common when plugins manage their own records, like events, contacts, or custom logs.

🎯 Goal: Build a WordPress plugin that creates a custom database table on activation and inserts data into it.

📋 What You'll Learn

Create a function to set up a custom database table named wp_custom_data with columns id (primary key, auto-increment) and info (text).

Use the WordPress dbDelta function to create or update the table.

Add an activation hook to run the table creation function.

Insert a sample row with info value 'Hello World' into the custom table.

💡 Why This Matters

🌍 Real World

Many WordPress plugins need their own tables to store custom data efficiently and separately from posts or options.

💼 Career

Understanding how to create and manage plugin database tables is essential for WordPress plugin developers and backend engineers working with WordPress.

1

Create the database table setup function

Write a function called create_custom_table that uses the global $wpdb variable and sets a variable $table_name to $wpdb->prefix . 'custom_data'. Define a SQL string $charset_collate using $wpdb->get_charset_collate(). Then create a SQL statement $sql to create a table with columns id as mediumint(9) NOT NULL AUTO_INCREMENT PRIMARY KEY and info as text NOT NULL. Use dbDelta to run the SQL.

Wordpress

# Your code here to create the function create_custom_table

Need a hint?

Remember to use dbDelta to create or update the table safely.

2

Add activation hook to create the table

Add a WordPress activation hook using register_activation_hook that calls the create_custom_table function when the plugin is activated. Use __FILE__ as the first argument.

Wordpress

prefix . 'custom_data';
    $charset_collate = $wpdb->get_charset_collate();

    $sql = "CREATE TABLE $table_name (
        id mediumint(9) NOT NULL AUTO_INCREMENT,
        info text NOT NULL,
        PRIMARY KEY  (id)
    ) $charset_collate;";

    require_once( ABSPATH . 'wp-admin/includes/upgrade.php' );
    dbDelta( $sql );
}

// Add activation hook here

Need a hint?

Use register_activation_hook with __FILE__ and the function name.

3

Insert a sample row into the custom table

Inside the create_custom_table function, after calling dbDelta, insert a new row into the $table_name table with the info column set to 'Hello World' using $wpdb->insert.

Wordpress

prefix . 'custom_data';
    $charset_collate = $wpdb->get_charset_collate();

    $sql = "CREATE TABLE $table_name (
        id mediumint(9) NOT NULL AUTO_INCREMENT,
        info text NOT NULL,
        PRIMARY KEY  (id)
    ) $charset_collate;";

    require_once( ABSPATH . 'wp-admin/includes/upgrade.php' );
    dbDelta( $sql );

    // Insert sample row here
}

register_activation_hook( __FILE__, 'create_custom_table' );

Need a hint?

Use $wpdb->insert with the table name and data array.

4

Complete the plugin file with header and closing PHP tag

Add the WordPress plugin header comment at the top of the file with Plugin Name: Custom Data Table. Also, ensure the PHP file ends properly without extra closing tags.

Wordpress

prefix . 'custom_data';
    $charset_collate = $wpdb->get_charset_collate();

    $sql = "CREATE TABLE $table_name (
        id mediumint(9) NOT NULL AUTO_INCREMENT,
        info text NOT NULL,
        PRIMARY KEY  (id)
    ) $charset_collate;";

    require_once( ABSPATH . 'wp-admin/includes/upgrade.php' );
    dbDelta( $sql );

    $wpdb->insert(
        $table_name,
        array('info' => 'Hello World'),
        array('%s')
    );
}

register_activation_hook( __FILE__, 'create_custom_table' );

Need a hint?

The plugin header comment must be at the very top of the file.