Understanding Laravel Generated Columns

Laravel, a popular PHP framework, is well known for its simplicity and powerful features. One feature that not many developers might be familiar with is Generated Columns. This concept allows developers to create virtual columns that automatically calculate their values based on other columns in the same table. By using generated columns in Laravel, you can enhance database efficiency and reduce the need for repetitive computations in your application.

In this article, we’ll explore what generated columns are, how they work, and how you can implement them in your Laravel projects.

What Are Generated Columns?

Generated columns are special columns in a database table whose values are calculated based on other columns in the table. The value of a generated column can be automatically updated when the columns it depends on are updated. This feature is supported by popular databases like MySQL, MariaDB, PostgreSQL, and SQLite.

There are two types of generated columns:

1. Virtual Columns: The value is calculated on the fly and does not physically exist in the database.
2. Stored Columns: The value is calculated once and physically stored in the database.

Laravel supports this feature via migrations, making it easy to define generated columns in your database schema.

Benefits of Using Generated Columns

Generated columns offer several advantages:

• Improved Performance: Since the column values are pre-calculated (stored columns) or computed dynamically (virtual columns), you avoid recalculating the same value multiple times during a query.
• Simplified Code: You can shift business logic from your Laravel models or controllers to the database, keeping your code cleaner.
• Consistency: Generated columns help maintain data consistency because their values always derive from the same source columns.

Implementing Generated Columns in Laravel

In Laravel, generated columns can be defined in migration files. Let’s look at how to create a generated column using Laravel’s migration system.

Step 1: Create a Migration

To create a migration file in Laravel, you can use the make:migration command:

php artisan make:migration add_generated_column_to_products_table

This command will generate a new migration file where you can define the schema changes.

Step 2: Define the Generated Column

In your migration file, you can define a new column that will calculate its value based on other columns in the same table. Here is an example where we create a table called products with unit_price, quantity, and a generated column full_price which is calculated as unit_price * quantity.

public function up(): void
{
    Schema::create('products', function (Blueprint $table) {
        $table->decimal('unit_price');
        $table->integer('quantity');

        // Create a generated column for full price
        $table->decimal('full_price')->storedAs('unit_price * quantity');
    });
}

In this example:

• unit_price is a regular decimal column.
• quantity is an integer column.
• full_price is a stored generated column that automatically calculates the product of unit_price and quantity.

Step 3: Running the Migration

After defining the migration, you can run the migration using:

php artisan migrate

This command will create the products table with the generated column full_price.

Step 4: Querying the Generated Column

Once the generated column is created, you can query it like any other column in your Laravel models. For instance, you can fetch the full_price for all products using:

$products = Product::all();

foreach ($products as $product) {
    echo $product->full_price;
}

Databases Supporting Generated Columns

Before implementing generated columns, it’s important to know which databases support this feature. Laravel’s migrations for generated columns work with the following databases:

• MariaDB: Generated columns are supported from version 5.2.
• MySQL: Supported from version 5.7.
• PostgreSQL: From version 12 and onwards.
• SQLite: Generated columns are supported from version 3.31.0.

Make sure that your database supports generated columns before attempting to implement them.