Laravel migration is a database version control tool that uses code to manage database structure changes. 1. Migrate Git like "Database" to record operations such as creating tables, adding columns, etc., to facilitate team collaboration and rollback. 2. Use the Artisan command to create a migration file, such as php artisan make:migration create_users_table, and you can specify the operation type through --create or --table. 3. In the migration file, the up() method defines structure changes, and down() is used for rollback. 4. Use php artisan migrate to perform migration, and you can use --path to specify a specific file. 5. Use migrate:rollback to rollback the previous migration, use migrate:reset to rollback, and use migrate:refresh to redo all migrations. 6. Practical suggestions include naming specifications, avoiding manual library modification, filling data with Seeder, paying attention to field length and foreign key constraints. Although migration is a bit complicated to beginners, it can significantly reduce communication and deployment costs.

Laravel's Migrations is a database version control tool. Simply put, it is to use code to manage changes in database structure. It allows you to define the table structure like writing code and synchronize these changes between different environments, such as when migrating from a development environment to a production environment, there will be no problems due to inconsistent database structures.

What is Laravel migration?

You can understand migration as "Git of the database". Every time you create a new table or modify a field, you can generate a migration file. This file records the operations you want to perform, such as creating tables, adding columns, deleting indexes, etc.

The benefits of doing this are:

• No need to manually modify the database structure
• Teamwork is more convenient, everyone uses the same migration script to operate the database
• Can rollback operations to avoid data loss due to incorrect operations

For example: If you want to create a user table now, you only need to run a command, Laravel will automatically generate the migration file and corresponding operation logic for you.

How to create and run a migration?

Laravel provides Artisan command line tools to help you quickly create and execute migrations.

Create a migration file:

 php artisan make:migration create_users_table

You can also include the --create or --table parameters to specify whether to create a new table or modify an existing table:

 php artisan make:migration create_posts_table --create=posts
php artisan make:migration add_avatar_to_users_table --table=users

Write migration content:

Open the generated migration file and you will see two methods: up() and down() .

• up() is used to apply changes, such as creating tables or adding fields
• down() is a rollback operation, such as deleting a table or field

For example, create a user table:

 public function up()
{
    Schema::create('users', function (Blueprint $table) {
        $table->id();
        $table->string('name');
        $table->string('email')->unique();
        $table->timestamps();
    });
}

Perform a migration:

After saving, run the following command to perform migration:

 php artisan migrate

If you want to run only a migration file, you can specify the path with the --path parameter.

How to rollback and redo migration?

What to do if there is a migration error? Laravel provides rollback functionality.

Roll back to the last migration:

 php artisan migrate:rollback

Roll back all migrations:

 php artisan migrate:reset

Roll back and rerun all migrations:

 php artisan migrate:refresh

These commands are especially useful during the debugging phase, especially when adjusting the field type or index.

Some tips for practical use

• Naming specifications are important : migration file names should clearly state what is done, such as add_status_to_orders_table .
• Try not to manually change the database structure : otherwise, the migration file and the actual structure will be inconsistent and errors will be prone to occur.
• Use it in conjunction with model factory and seed filling : After the migration is completed, you can use Seeder to insert the test data.
• Pay attention to the field length and default value : For example, the default string is 255. If it is not enough, use text or custom length.
• Remember to deal with foreign key constraints : use $table->foreignId() to establish foreign key relationships to avoid data consistency issues.

Basically that's it. Migration is not a black technology, but it is a very practical tool for organizing database structures in Laravel. It may feel troublesome at first, but after using it a few times, you will find that it can save a lot of communication and deployment costs.

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