# 數據庫遷移（Database Migrations） # 數據庫遷移（Database Migrations） Migrations are a convenient way for you to alter your database in a structured and organized manner. > **Important:** Migrations are available on [*Phalcon Developer Tools*](#) You need at least Phalcon Framework version 0.5.0 to use developer tools. Also, it is recommended to have PHP 5.4 or greater installed. Often in development we need to update changes in production environments. Some of these changes could be database modifications like new fields, new tables, removing indexes, etc. When a migration is generated a set of classes are created to describe how your database is structured at that moment. These classes can be used to synchronize the schema structure on remote databases setting your database ready to work with the new changes that your application implements. Migrations describe these transformations using plain PHP. ### 圖解導出（Schema Dumping） The [*Phalcon Developer Tools*](#) provides scripts to manage migrations (generation, running and rollback). The available options for generating migrations are:  Running this script without any parameters will simply dump every object (tables and views) from your database in migration classes. Each migration has a version identifier associated to it. The version number allows us to identify if the migration is newer or older than the current ‘version' of our database. Versions also inform Phalcon of the running order when executing a migration.  When a migration is generated, instructions are displayed on the console to describe the different steps of the migration and the execution time of those statements. At the end, a migration version is generated. By default [*Phalcon Developer Tools*](#) use the *app/migrations* directory to dump the migration files. You can change the location by setting one of the parameters on the generation script. Each table in the database has its respective class generated in a separated file under a directory referring its version:  ### 遷移類剖析（Migration Class Anatomy） Each file contains a unique class that extends the Phalcon\\Mvc\\Model\\Migration These classes normally have two methods: up() and down(). Up() performs the migration, while down() rolls it back. Up() also contains the *magic* method morphTable(). The magic comes when it recognizes the changes needed to synchronize the actual table in the database to the description given. ``` <pre class="calibre14">``` <?php use Phalcon\Db\Column as Column; use Phalcon\Db\Index as Index; use Phalcon\Db\Reference as Reference; class ProductsMigration_100 extends \Phalcon\Mvc\Model\Migration { public function up() { $this->morphTable( "products", array( "columns" => array( new Column( "id", array( "type" => Column::TYPE_INTEGER, "size" => 10, "unsigned" => true, "notNull" => true, "autoIncrement" => true, "first" => true ) ), new Column( "product_types_id", array( "type" => Column::TYPE_INTEGER, "size" => 10, "unsigned" => true, "notNull" => true, "after" => "id" ) ), new Column( "name", array( "type" => Column::TYPE_VARCHAR, "size" => 70, "notNull" => true, "after" => "product_types_id" ) ), new Column( "price", array( "type" => Column::TYPE_DECIMAL, "size" => 16, "scale" => 2, "notNull" => true, "after" => "name" ) ), ), "indexes" => array( new Index( "PRIMARY", array("id") ), new Index( "product_types_id", array("product_types_id") ) ), "references" => array( new Reference( "products_ibfk_1", array( "referencedSchema" => "invo", "referencedTable" => "product_types", "columns" => array("product_types_id"), "referencedColumns" => array("id") ) ) ), "options" => array( "TABLE_TYPE" => "BASE TABLE", "ENGINE" => "InnoDB", "TABLE_COLLATION" => "utf8_general_ci" ) ) ); } } ``` ``` The class is called “ProductsMigration\_100”. Suffix 100 refers to the version 1.0.0. morphTable() receives an associative array with 4 possible sections: IndexDescriptionOptional“columns”An array with a set of table columnsNo“indexes”An array with a set of table indexes.Yes“references”An array with a set of table references (foreign keys).Yes“options”An array with a set of table creation options. These options are often related to the database system in which the migration was generated.Yes### 定義列（Defining Columns） [*Phalcon\\Db\\Column*](#) is used to define table columns. It encapsulates a wide variety of column related features. Its constructor receives as first parameter the column name and an array describing the column. The following options are available when describing columns: OptionDescriptionOptional“type”Column type. Must be a [*Phalcon\_Db\_Column*](#) constant (see below)No“size”Some type of columns like VARCHAR or INTEGER may have a specific sizeYes“scale”DECIMAL or NUMBER columns may be have a scale to specify how much decimals it must storeYes“unsigned”INTEGER columns may be signed or unsigned. This option does not apply to other types of columnsYes“notNull”Column can store null values?Yes“autoIncrement”With this attribute column will filled automatically with an auto-increment integer. Only one column in the table can have this attribute.Yes“first”Column must be placed at first position in the column orderYes“after”Column must be placed after indicated columnYesDatabase migrations support the following database column types: - Phalcon\\Db\\Column::TYPE\_INTEGER - Phalcon\\Db\\Column::TYPE\_DATE - Phalcon\\Db\\Column::TYPE\_VARCHAR - Phalcon\\Db\\Column::TYPE\_DECIMAL - Phalcon\\Db\\Column::TYPE\_DATETIME - Phalcon\\Db\\Column::TYPE\_CHAR - Phalcon\\Db\\Column::TYPE\_TEXT ### 定義索引（Defining Indexes） [*Phalcon\\Db\\Index*](#) defines table indexes. An index only requires that you define a name for it and a list of its columns. Note that if any index has the name PRIMARY, Phalcon will create a primary key index in that table. ### 定義關系（Defining References） [*Phalcon\\Db\\Reference*](#) defines table references (also called foreign keys). The following options can be used to define a reference: IndexDescriptionOptional“referencedTable”It's auto-descriptive. It refers to the name of the referenced table.No“columns”An array with the name of the columns at the table that have the referenceNo“referencedColumns”An array with the name of the columns at the referenced tableNo“referencedTable”The referenced table maybe is on another schema or database. This option allows you to define that.Yes### 創建遷移類（Writing Migrations） Migrations aren't only designed to “morph” table. A migration is just a regular PHP class so you're not limited to these functions. For example after adding a column you could write code to set the value of that column for existing records. For more details and examples of individual methods, check the [*database component*](#). ``` <pre class="calibre14">``` <?php class ProductsMigration_100 extends \Phalcon\Mvc\Model\Migration { public function up() { // ... self::$_connection->insert( "products", array("Malabar spinach", 14.50), array("name", "price") ); } } ``` ``` ### 執行遷移（Running Migrations） Once the generated migrations are uploaded on the target server, you can easily run them as shown in the following example:   Depending on how outdated is the database with respect to migrations, Phalcon may run multiple migration versions in the same migration process. If you specify a target version, Phalcon will run the required migrations until it reaches the specified version. | - [索引](# "總目錄") - [下一頁](# "調試應用程序（Debugging Applications）") | - [上一頁](# "國際化（Internationalization）") |