# Class yii\db\Migration

Inheritance | yii\db\Migration » yii\base\Component » yii\base\BaseObject
Implements | yii\base\Configurable, yii\db\MigrationInterface
Uses Traits | yii\db\SchemaBuilderTrait
Available since version | 2.0
Source Code | https://github.com/yiisoft/yii2/blob/master/framework/db/Migration.php

Migration is the base class for representing a database migration.

Migration is designed to be used together with the "yii migrate" command.

Each child class of Migration represents an individual database migration which is identified by the child class name.

Within each migration, the up() method should be overridden to contain the logic for "upgrading" the database; while the down() method for the "downgrading" logic. The "yii migrate" command manages all available migrations in an application.

If the database supports transactions, you may also override safeUp() and safeDown() so that if anything wrong happens during the upgrading or downgrading, the whole migration can be reverted in a whole.

Note that some DB queries in some DBMS cannot be put into a transaction. For some examples, please refer to implicit commit. If this is the case, you should still implement `up()` and `down()`, instead.

Migration provides a set of convenient methods for manipulating database data and schema. For example, the insert() method can be used to easily insert a row of data into a database table; the createTable() method can be used to create a database table. Compared with the same methods in yii\db\Command, these methods will display extra information showing the method parameters and execution time, which may be useful when applying migrations.

For more details and usage information on Migration, see the guide article on Migration.

## Public Properties

Hide inherited properties

Property | Type | Description | Defined By
--- | --- | --- | ---
$behaviors | yii\base\Behavior[] | List of behaviors attached to this component. This property is read-only. | yii\base\Component
$compact | boolean | Indicates whether the console output should be compacted. | yii\db\Migration
$db | yii\db\Connection|array|string | The DB connection object or the application component ID of the DB connection that this migration should work with. | yii\db\Migration
$maxSqlOutputLength | integer | Max number of characters of the SQL outputted. | yii\db\Migration

## Public Methods

Hide inherited methods

Method | Description | Defined By
--- | --- | ---
__call() | Calls the named method which is not a class method. | yii\base\Component
__clone() | This method is called after the object is created by cloning an existing one. | yii\base\Component
__construct() | Constructor. | yii\base\BaseObject
__get() | Returns the value of a component property. | yii\base\Component
__isset() | Checks if a property is set, i.e. defined and not null. | yii\base\Component
__set() | Sets the value of a component property. | yii\base\Component
__unset() | Sets a component property to be null. | yii\base\Component
addColumn() | Builds and executes a SQL statement for adding a new DB column. | yii\db\Migration
addCommentOnColumn() | Builds and execute a SQL statement for adding comment to column. | yii\db\Migration
addCommentOnTable() | Builds a SQL statement for adding comment to table. | yii\db\Migration
addForeignKey() | Builds a SQL statement for adding a foreign key constraint to an existing table. | yii\db\Migration
addPrimaryKey() | Builds and executes a SQL statement for creating a primary key. | yii\db\Migration
alterColumn() | Builds and executes a SQL statement for changing the definition of a column. | yii\db\Migration
attachBehavior() | Attaches a behavior to this component. | yii\base\Component
attachBehaviors() | Attaches a list of behaviors to the component. | yii\base\Component
batchInsert() | Creates and executes a batch INSERT SQL statement. | yii\db\Migration
behaviors() | Returns a list of behaviors that this component should behave as. | yii\base\Component
bigInteger() | Creates a bigint column. | yii\db\SchemaBuilderTrait
bigPrimaryKey() | Creates a big primary key column. | yii\db\SchemaBuilderTrait
binary() | Creates a binary column. | yii\db\SchemaBuilderTrait
boolean() | Creates a boolean column. | yii\db\SchemaBuilderTrait
canGetProperty() | Returns a value indicating whether a property can be read. | yii\base\Component
canSetProperty() | Returns a value indicating whether a property can be set. | yii\base\Component
char() | Creates a char column. | yii\db\SchemaBuilderTrait
className() | Returns the fully qualified name of this class. | yii\base\BaseObject
createIndex() | Builds and executes a SQL statement for creating a new index. | yii\db\Migration
createTable() | Builds and executes a SQL statement for creating a new DB table. | yii\db\Migration
date() | Creates a date column. | yii\db\SchemaBuilderTrait
dateTime() | Creates a datetime column. | yii\db\SchemaBuilderTrait
decimal() | Creates a decimal column. | yii\db\SchemaBuilderTrait
delete() | Creates and executes a DELETE SQL statement. | yii\db\Migration
detachBehavior() | Detaches a behavior from the component. | yii\base\Component
detachBehaviors() | Detaches all behaviors from the component. | yii\base\Component
double() | Creates a double column. | yii\db\SchemaBuilderTrait
down() | This method contains the logic to be executed when removing this migration. | yii\db\Migration
dropColumn() | Builds and executes a SQL statement for dropping a DB column. | yii\db\Migration
dropCommentFromColumn() | Builds and execute a SQL statement for dropping comment from column. | yii\db\Migration
dropCommentFromTable() | Builds a SQL statement for dropping comment from table. | yii\db\Migration
dropForeignKey() | Builds a SQL statement for dropping a foreign key constraint. | yii\db\Migration
dropIndex() | Builds and executes a SQL statement for dropping an index. | yii\db\Migration
dropPrimaryKey() | Builds and executes a SQL statement for dropping a primary key. | yii\db\Migration
dropTable() | Builds and executes a SQL statement for dropping a DB table. | yii\db\Migration
ensureBehaviors() | Makes sure that the behaviors declared in behaviors() are attached to this component. | yii\base\Component
execute() | Executes a SQL statement. | yii\db\Migration
float() | Creates a float column. | yii\db\SchemaBuilderTrait
getBehavior() | Returns the named behavior object. | yii\base\Component
getBehaviors() | Returns all behaviors attached to this component. | yii\base\Component
hasEventHandlers() | Returns a value indicating whether there is any handler attached to the named event. | yii\base\Component
hasMethod() | Returns a value indicating whether a method is defined. | yii\base\Component
hasProperty() | Returns a value indicating whether a property is defined for this component. | yii\base\Component
init() | Initializes the migration. | yii\db\Migration
insert() | Creates and executes an INSERT SQL statement. | yii\db\Migration
integer() | Creates an integer column. | yii\db\SchemaBuilderTrait
json() | Creates a JSON column. | yii\db\SchemaBuilderTrait
money() | Creates a money column. | yii\db\SchemaBuilderTrait
off() | Detaches an existing event handler from this component. | yii\base\Component
on() | Attaches an event handler to an event. | yii\base\Component
primaryKey() | Creates a primary key column. | yii\db\SchemaBuilderTrait
renameColumn() | Builds and executes a SQL statement for renaming a column. | yii\db\Migration
renameTable() | Builds and executes a SQL statement for renaming a DB table. | yii\db\Migration
safeDown() | This method contains the logic to be executed when removing this migration. | yii\db\Migration
safeUp() | This method contains the logic to be executed when applying this migration. | yii\db\Migration
smallInteger() | Creates a smallint column. | yii\db\SchemaBuilderTrait
string() | Creates a string column. | yii\db\SchemaBuilderTrait
text() | Creates a text column. | yii\db\SchemaBuilderTrait
time() | Creates a time column. | yii\db\SchemaBuilderTrait
timestamp() | Creates a timestamp column. | yii\db\SchemaBuilderTrait
tinyInteger() | Creates a tinyint column. If tinyint is not supported by the DBMS, smallint will be used. | yii\db\SchemaBuilderTrait
trigger() | Triggers an event. | yii\base\Component
truncateTable() | Builds and executes a SQL statement for truncating a DB table. | yii\db\Migration
up() | This method contains the logic to be executed when applying this migration. | yii\db\Migration
update() | Creates and executes an UPDATE SQL statement. | yii\db\Migration
upsert() | Creates and executes a command to insert rows into a database table if they do not already exist (matching unique constraints), or update them if they do. | yii\db\Migration

## Protected Methods

Hide inherited methods

Method | Description | Defined By
--- | --- | ---
beginCommand() | Prepares for a command to be executed, and outputs to the console. | yii\db\Migration
endCommand() | Finalizes after the command has been executed, and outputs to the console the time elapsed. | yii\db\Migration
getDb() |  | yii\db\Migration

## Property Details

$compact public property (available since version 2.0.13)

Indicates whether the console output should be compacted. If this is set to true, the individual commands ran within the migration will not be output to the console. Default is false, in other words the output is fully verbose by default.

public boolean $compact = false
$db public property

The DB connection object or the application component ID of the DB connection that this migration should work with. Starting from version 2.0.2, this can also be a configuration array for creating the object.

Note that when a Migration object is created by the `migrate` command, this property will be overwritten by the command. If you do not want to use the DB connection provided by the command, you may override the init() method like the following:

    public function init()
    {
        $this->db = 'db2';
        parent::init();
    }

public yii\db\Connection|array|string $db = 'db'
$maxSqlOutputLength public property (available since version 2.0.13)

Max number of characters of the SQL outputted. Useful for reduction of long statements and making console output more compact.

public integer $maxSqlOutputLength = null

## Method Details

addColumn() public method

Builds and executes a SQL statement for adding a new DB column.

public void addColumn ( $table, $column, $type )
$table | string | The table that the new column will be added to. The table name will be properly quoted by the method.
$column | string | The name of the new column. The name will be properly quoted by the method.
$type | string | The column type. The yii\db\QueryBuilder::getColumnType() method will be invoked to convert abstract column type (if any) into the physical one. Anything that is not recognized as abstract type will be kept in the generated SQL. For example, 'string' will be turned into 'varchar(255)', while 'string not null' will become 'varchar(255) not null'.

addCommentOnColumn() public method (available since version 2.0.8)

Builds and execute a SQL statement for adding comment to column.

public void addCommentOnColumn ( $table, $column, $comment )
$table | string | The table whose column is to be commented. The table name will be properly quoted by the method.
$column | string | The name of the column to be commented. The column name will be properly quoted by the method.
$comment | string | The text of the comment to be added. The comment will be properly quoted by the method.

addCommentOnTable() public method (available since version 2.0.8)

Builds a SQL statement for adding comment to table.

public void addCommentOnTable ( $table, $comment )
$table | string | The table to be commented. The table name will be properly quoted by the method.
$comment | string | The text of the comment to be added. The comment will be properly quoted by the method.

addForeignKey() public method

Builds a SQL statement for adding a foreign key constraint to an existing table.

The method will properly quote the table and column names.

public void addForeignKey ( $name, $table, $columns, $refTable, $refColumns, $delete = null, $update = null )
$name | string | The name of the foreign key constraint.
$table | string | The table that the foreign key constraint will be added to.
$columns | string|array | The name of the column to that the constraint will be added on. If there are multiple columns, separate them with commas or use an array.
$refTable | string | The table that the foreign key references to.
$refColumns | string|array | The name of the column that the foreign key references to. If there are multiple columns, separate them with commas or use an array.
$delete | string | The ON DELETE option. Most DBMS support these options: RESTRICT, CASCADE, NO ACTION, SET DEFAULT, SET NULL
$update | string | The ON UPDATE option. Most DBMS support these options: RESTRICT, CASCADE, NO ACTION, SET DEFAULT, SET NULL

addPrimaryKey() public method

Builds and executes a SQL statement for creating a primary key.

The method will properly quote the table and column names.

public void addPrimaryKey ( $name, $table, $columns )
$name | string | The name of the primary key constraint.
$table | string | The table that the primary key constraint will be added to.
$columns | string|array | Comma separated string or array of columns that the primary key will consist of.

alterColumn() public method

Builds and executes a SQL statement for changing the definition of a column.

public void alterColumn ( $table, $column, $type )
$table | string | The table whose column is to be changed. The table name will be properly quoted by the method.
$column | string | The name of the column to be changed. The name will be properly quoted by the method.
$type | string | The new column type. The yii\db\QueryBuilder::getColumnType() method will be invoked to convert abstract column type (if any) into the physical one. Anything that is not recognized as abstract type will be kept in the generated SQL. For example, 'string' will be turned into 'varchar(255)', while 'string not null' will become 'varchar(255) not null'.

batchInsert() public method

Creates and executes a batch INSERT SQL statement.

The method will properly escape the column names, and bind the values to be inserted.

public void batchInsert ( $table, $columns, $rows )
$table | string | The table that new rows will be inserted into.
$columns | array | The column names.
$rows | array | The rows to be batch inserted into the table

beginCommand() protected method (available since version 2.0.13)

Prepares for a command to be executed, and outputs to the console.

protected float beginCommand ( $description )
$description | string | The description for the command, to be output to the console.
return | float | The time before the command is executed, for the time elapsed to be calculated.

createIndex() public method

Builds and executes a SQL statement for creating a new index.

public void createIndex ( $name, $table, $columns, $unique = false )
$name | string | The name of the index. The name will be properly quoted by the method.
$table | string | The table that the new index will be created for. The table name will be properly quoted by the method.
$columns | string|array | The column(s) that should be included in the index. If there are multiple columns, please separate them by commas or use an array. Each column name will be properly quoted by the method. Quoting will be skipped for column names that include a left parenthesis "(".
$unique | boolean | Whether to add UNIQUE constraint on the created index.

createTable() public method

Builds and executes a SQL statement for creating a new DB table.

The columns in the new table should be specified as name-definition pairs (e.g. 'name' => 'string'), where name stands for a column name which will be properly quoted by the method, and definition stands for the column type which can contain an abstract DB type.

The yii\db\QueryBuilder::getColumnType() method will be invoked to convert any abstract type into a physical one.

If a column is specified with definition only (e.g. 'PRIMARY KEY (name, type)'), it will be directly put into the generated SQL.

public void createTable ( $table, $columns, $options = null )
$table | string | The name of the table to be created. The name will be properly quoted by the method.
$columns | array | The columns (name => definition) in the new table.
$options | string | Additional SQL fragment that will be appended to the generated SQL.

delete() public method

Creates and executes a DELETE SQL statement.

public void delete ( $table, $condition = '', $params = [] )
$table | string | The table where the data will be deleted from.
$condition | array|string | The conditions that will be put in the WHERE part. Please refer to yii\db\Query::where() on how to specify conditions.
$params | array | The parameters to be bound to the query.

down() public method

This method contains the logic to be executed when removing this migration.

The default implementation throws an exception indicating the migration cannot be removed. Child classes may override this method if the corresponding migrations can be removed.

public boolean down ( )
return | boolean | Return a false value to indicate the migration fails and should not proceed further. All other return values mean the migration succeeds.

dropColumn() public method

Builds and executes a SQL statement for dropping a DB column.

public void dropColumn ( $table, $column )
$table | string | The table whose column is to be dropped. The name will be properly quoted by the method.
$column | string | The name of the column to be dropped. The name will be properly quoted by the method.

dropCommentFromColumn() public method (available since version 2.0.8)

Builds and execute a SQL statement for dropping comment from column.

public void dropCommentFromColumn ( $table, $column )
$table | string | The table whose column is to be commented. The table name will be properly quoted by the method.
$column | string | The name of the column to be commented. The column name will be properly quoted by the method.

dropCommentFromTable() public method (available since version 2.0.8)

Builds a SQL statement for dropping comment from table.

public void dropCommentFromTable ( $table )
$table | string | The table whose column is to be commented. The table name will be properly quoted by the method.

dropForeignKey() public method

Builds a SQL statement for dropping a foreign key constraint.

public void dropForeignKey ( $name, $table )
$name | string | The name of the foreign key constraint to be dropped. The name will be properly quoted by the method.
$table | string | The table whose foreign is to be dropped. The name will be properly quoted by the method.

dropIndex() public method

Builds and executes a SQL statement for dropping an index.

public void dropIndex ( $name, $table )
$name | string | The name of the index to be dropped. The name will be properly quoted by the method.
$table | string | The table whose index is to be dropped. The name will be properly quoted by the method.

dropPrimaryKey() public method

Builds and executes a SQL statement for dropping a primary key.

public void dropPrimaryKey ( $name, $table )
$name | string | The name of the primary key constraint to be removed.
$table | string | The table that the primary key constraint will be removed from.

dropTable() public method

Builds and executes a SQL statement for dropping a DB table.

public void dropTable ( $table )
$table | string | The table to be dropped. The name will be properly quoted by the method.

endCommand() protected method (available since version 2.0.13)

Finalizes after the command has been executed, and outputs to the console the time elapsed.

protected void endCommand ( $time )
$time | float | The time before the command was executed.

execute() public method

Executes a SQL statement.

This method executes the specified SQL statement using $db.

public void execute ( $sql, $params = [] )
$sql | string | The SQL statement to be executed
$params | array | Input parameters (name => value) for the SQL execution. See yii\db\Command::execute() for more details.

getDb() protected method (available since version 2.0.6)

protected void getDb ( )

init() public method

Initializes the migration.

This method will set $db to be the 'db' application component, if it is `null`.

public void init ( )

insert() public method

Creates and executes an INSERT SQL statement.

The method will properly escape the column names, and bind the values to be inserted.

public void insert ( $table, $columns )
$table | string | The table that new rows will be inserted into.
$columns | array | The column data (name => value) to be inserted into the table.

renameColumn() public method

Builds and executes a SQL statement for renaming a column.

public void renameColumn ( $table, $name, $newName )
$table | string | The table whose column is to be renamed. The name will be properly quoted by the method.
$name | string | The old name of the column. The name will be properly quoted by the method.
$newName | string | The new name of the column. The name will be properly quoted by the method.

renameTable() public method

Builds and executes a SQL statement for renaming a DB table.

public void renameTable ( $table, $newName )
$table | string | The table to be renamed. The name will be properly quoted by the method.
$newName | string | The new table name. The name will be properly quoted by the method.

safeDown() public method

This method contains the logic to be executed when removing this migration.

This method differs from down() in that the DB logic implemented here will be enclosed within a DB transaction. Child classes may implement this method instead of down() if the DB logic needs to be within a transaction.

Note: Not all DBMS support transactions. And some DB queries cannot be put into a transaction. For some examples, please refer to implicit commit.

public boolean safeDown ( )
return | boolean | Return a false value to indicate the migration fails and should not proceed further. All other return values mean the migration succeeds.

safeUp() public method

This method contains the logic to be executed when applying this migration.

This method differs from up() in that the DB logic implemented here will be enclosed within a DB transaction. Child classes may implement this method instead of up() if the DB logic needs to be within a transaction.

Note: Not all DBMS support transactions. And some DB queries cannot be put into a transaction. For some examples, please refer to implicit commit.

public boolean safeUp ( )
return | boolean | Return a false value to indicate the migration fails and should not proceed further. All other return values mean the migration succeeds.

truncateTable() public method

Builds and executes a SQL statement for truncating a DB table.

public void truncateTable ( $table )
$table | string | The table to be truncated. The name will be properly quoted by the method.

up() public method

This method contains the logic to be executed when applying this migration.

Child classes may override this method to provide actual migration logic.

public boolean up ( )
return | boolean | Return a false value to indicate the migration fails and should not proceed further. All other return values mean the migration succeeds.

update() public method

Creates and executes an UPDATE SQL statement.

The method will properly escape the column names and bind the values to be updated.

public void update ( $table, $columns, $condition = '', $params = [] )
$table | string | The table to be updated.
$columns | array | The column data (name => value) to be updated.
$condition | array|string | The conditions that will be put in the WHERE part. Please refer to yii\db\Query::where() on how to specify conditions.
$params | array | The parameters to be bound to the query.

upsert() public method (available since version 2.0.14)

Creates and executes a command to insert rows into a database table if they do not already exist (matching unique constraints), or update them if they do.

The method will properly escape the column names, and bind the values to be inserted.

public $this upsert ( $table, $insertColumns, $updateColumns = true, $params = [] )
$table | string | The table that new rows will be inserted into/updated in.
$insertColumns | array|yii\db\Query | The column data (name => value) to be inserted into the table or instance of yii\db\Query to perform `INSERT INTO ... SELECT` SQL statement.
$updateColumns | array|boolean | The column data (name => value) to be updated if they already exist. If `true` is passed, the column data will be updated to match the insert column data. If `false` is passed, no update will be performed if the column data already exists.
$params | array | The parameters to be bound to the command.
return | $this | The command object itself.