Plugin database tables in Wordpress - Step-by-Step Execution

Concept Flow - Plugin database tables

Plugin Activation

↓

Check if DB Tables Exist?

Yes→Skip Creation

No↓

Create Plugin DB Tables

↓

Store Table Names & Versions

↓

Plugin Uses Tables for Data Storage

↓

Plugin Deactivation or Update

↓

Optional: Update or Remove Tables

When a plugin activates, it checks if its database tables exist. If not, it creates them, stores info, and uses them for data. On updates or deactivation, it may update or remove tables.

Execution Sample

Wordpress

<?php
function plugin_activate() {
  global $wpdb;
  $table_name = $wpdb->prefix . 'myplugin_data';
  if($wpdb->get_var("SHOW TABLES LIKE '$table_name'") != $table_name) {
    $charset_collate = $wpdb->get_charset_collate();
    $sql = "CREATE TABLE $table_name (id mediumint(9) NOT NULL AUTO_INCREMENT, data text NOT NULL, PRIMARY KEY  (id)) $charset_collate;";
    require_once(ABSPATH . 'wp-admin/includes/upgrade.php');
    dbDelta($sql);
    add_option('myplugin_db_version', '1.0');
  }
}

This code runs on plugin activation to create a custom database table if it doesn't exist.

Execution Table

Step	Action	Check	Result	Next Step
1	Plugin activates	N/A	Start activation	Check if table exists
2	Check table existence	SHOW TABLES LIKE 'wp_myplugin_data'	Table not found	Create table
3	Create table SQL prepared	N/A	SQL ready with charset	Run dbDelta()
4	Run dbDelta()	Execute CREATE TABLE	Table created successfully	Store version info
5	Store version info	N/A	Version saved in options	Activation complete
6	Activation complete	N/A	Plugin ready to use tables	End

💡 Table exists or created, activation finishes successfully

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
$table_name	undefined	wp_myplugin_data	wp_myplugin_data	wp_myplugin_data	wp_myplugin_data
$charset_collate	undefined	undefined	utf8mb4_unicode_ci	utf8mb4_unicode_ci	utf8mb4_unicode_ci
$sql	undefined	undefined	CREATE TABLE SQL string	CREATE TABLE SQL string	CREATE TABLE SQL string

Key Moments - 3 Insights

Why do we check if the table exists before creating it?

To avoid errors and duplicate tables, the plugin checks if the table already exists (see execution_table step 2). If it exists, creation is skipped.

What does dbDelta() do with the SQL?

dbDelta() runs the SQL safely, creating or updating the table structure without losing data (see execution_table step 4).

Why store the table version after creation?

Storing the version helps the plugin know if it needs to update the table structure later (see execution_table step 5).

Visual Quiz - 3 Questions

Look at the execution_table, what happens at step 2?

A The plugin checks if the database table exists

B The plugin creates the database table

C The plugin stores the version info

D The plugin finishes activation

💡 Hint

Refer to execution_table row with Step 2 describing the check for table existence

According to variable_tracker, what value does $charset_collate have after step 3?

A undefined

B utf8mb4_unicode_ci

C wp_myplugin_data

D CREATE TABLE SQL string

💡 Hint

Check variable_tracker row for $charset_collate at After Step 3 column

If the table already exists, which step in execution_table is skipped?

A Step 2

B Step 3

C Step 4

D Step 5

💡 Hint

Look at execution_table step 2 result 'Table not found' triggers creation at step 4; if table exists, creation (step 4) is skipped

Concept Snapshot

Plugin database tables:
- On activation, check if tables exist
- If not, create tables with dbDelta()
- Store version info for updates
- Use $wpdb->prefix for table names
- Use charset collate for compatibility
- Avoid duplicate tables by checking first

Full Transcript

When a WordPress plugin activates, it needs to store data in custom database tables. The plugin first checks if its tables already exist using a SQL query. If the tables do not exist, it prepares a CREATE TABLE SQL statement including the correct character set and collation. Then it runs the dbDelta() function to create or update the table safely. After creation, the plugin stores the table version in the WordPress options to track future updates. This process prevents errors from duplicate tables and ensures the plugin can manage its data storage properly. Variables like $table_name hold the full table name with prefix, and $charset_collate ensures the table uses the right encoding. This flow is essential for plugins that need custom data storage beyond WordPress default tables.