Laravel Migrations manages database structure changes through version control, supporting security upgrades and rollbacks. 1. Use the artisan command to create a migration file and specify to create or modify the table; 2. The up() method performs changes, and down() is used for rollback; 3. When modifying the table structure, you need to be careful of data corruption. You can add fields, delete fields or modify types (requires doctrine/dbal package); 4. Run the migrate command to perform migration, and rollback can be used for errors; 5. Pay attention to the field default values ??and timestamp customization and avoid manual database modification to maintain consistency.

Changes in database structure are inevitable when developing Laravel applications. Laravel Migrations provides a version-controlled way to manage these changes, allowing you to safely upgrade and roll back the database structure without affecting existing data. It's not all-purpose, but it's good enough for most projects.

Create a migration file: Start with the basics

Laravel provides the Artisan command to generate migration files, such as:

 php artisan make:migration create_users_table

This command will create a migration file with a timestamp and place it in database/migrations directory. You can specify whether to create a new table or modify an existing table by adding --create=table_name or --table=table_name parameter.

In the generated file, there are two core methods: up() and down() . The former is used to apply changes, and the latter is used to rollback. For example, adding fields, modifying field types, deleting indexes and other operations can all be completed here.

suggestion:

• Do only one thing at a time (such as adding one field at a time) so that rollback or debugging will be clearer in the future.
• Give the migration file a meaningful name for easier search.

Modify existing table structure: Be careful not to destroy existing data

When you need to add fields to existing tables or change the field type, you can use php artisan make:migration add_column_to_table --table=your_table_name to generate migration files.

Common operations include:

• Add fields: $table->string('email')->nullable();
• Delete field: $table->dropColumn('old_column');
• Modify field type: You need to install the doctrine/dbal package first, and then use $table->renameColumn() or $table->change()

?? Note:

• Before modifying the field type, it is best to confirm whether there is data in the current field, otherwise an error may occur.
• Not all databases support field renaming or modification types, and some versions of MySQL are more "stubborn".

Run and rollback migration: operations that must be mastered before going online

After creating the migration file, use the following command to execute:

 php artisan migrate

If you find that you have written it incorrectly, you can use:

 php artisan migrate:rollback

If you want to reset the entire database structure, you can:

 php artisan migrate:reset

Use the online environment with caution! Unless you have a full backup.

Tips:

• You can add --step parameter and roll back one step at a time.
• Use --path to specify migration files in a specific directory, suitable for modular projects.

Some small details that are easy to ignore

1. The field default value and NULL settings should be clear
   For example, set the field to be nullable: $table->string('name')->nullable();
   Or set the default value: $table->boolean('active')->default(true);

2. Timestamp fields can be customized
   By default, Laravel will automatically add created_at and updated_at , but you can also turn it off: $table->timestamps(false); or custom field names: $table->timestamps(0, ['created' => 'my_created', 'updated' => 'my_updated']);

3. Don't change the database structure manually easily
   Once migration is used, try to maintain consistency. Otherwise, it is easy to cause inconsistent local and server structures.

Basically that's it. Although Migration seems simple, if used properly, it will be of great help to long-term maintenance of the project.

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