The steps to create a migration in the Yii framework are as follows: 1. Use the yii migrate/create command to generate a migration template file, such as yii migrate/create create_user_table; 2. Write the up() method in the generated file to define the database change logic, such as using createTable() to create a table structure; 3. Implement the rollback operation in the down() method, such as dropTable() to delete the table; 4. Execute yii migrate to run all unexecuted migrations, or use yii migrate/up and yii migrate/down to control a single migration and rollback; 5. You can insert initial data in the migration with batchInsert and pay attention to field type compatibility to ensure that the migration runs normally in different databases.
Creating a new migration in the Yii framework is not complicated. The core is to use the command line tool provided by Yii to generate template files and then write the logic for database structure changes in it. Migration can help you version the database structure, making it easier for team collaboration and deployment.
Generate migration files using the command line
Yii provides the migrate/create command to generate an empty migration file. You can create a new migration through the following command:
yii migrate/create create_table_name
create_table_name here is the migration description you define yourself. For example, you can write it as create_user_table to create a user table. After execution, a file similar to m240501_123456_create_user_table.php will be generated in migrations/ directory.
Note: The migration file name begins with a timestamp, so that Yii can correctly identify the execution order.
Write up() and down() methods
There are two methods in the generated migration file: up() is used to apply changes, down() is used to roll back changes.
For example, if you want to create a user table, you can use createTable() method in up() :
public function up()
{
$this->createTable('user', [
'id' => $this->primaryKey(),
'username' => $this->string()->notNull(),
'email' => $this->string()->notNull(),
'created_at' => $this->integer(),
]);
} The corresponding down() method should do the opposite, such as deleting this table:
public function down()
{
$this->dropTable('user');
}Small suggestions: Try to make the
down()method rollback safely to avoid data loss. If some operations cannot be rolled back (such as deleting fields), you can throw an exception or add comment instructions.
Perform a migration
After completing the migration file, you can run the following command to perform the migration:
yii migrate
It lists all unexecuted migrations and asks whether to continue execution. Enter yes to complete the database structure update.
If you want to perform only the most recent migration, you can use:
yii migrate/up
Or roll back the last migration:
yii migrate/down
Practical tips
Multiple operations are put together : You can do multiple things in one migration, such as creating tables and inserting initial data at the same time.
Use batchInsert to insert multiple pieces of data :
$this->batchInsert('user', ['username', 'email'], [ ['admin', 'admin@example.com'], ['test', 'test@example.com'], ]);Note field type compatibility : The data types supported by different databases vary slightly to ensure that your migration code works properly on the target database.
Basically that's it. Although Yii's migration mechanism is simple, it is very practical. As long as you follow the steps, you will generally not make any mistakes.
The above is the detailed content of How do I create a new migration in Yii?. For more information, please follow other related articles on the PHP Chinese website!
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