Class CDbMigration

CDbMigration is the base class for representing a database migration.

CDbMigration is designed to be used together with the "yiic migrate" command.

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

Within each migration, the CDbMigration::up() method contains the logic for "upgrading" the database used in an application; while the CDbMigration::down() method contains "downgrading" logic. The "yiic migrate" command manages all available migrations in an application.

By overriding CDbMigration::safeUp() or CDbMigration::safeDown() methods instead of CDbMigration::up() and CDbMigration::down() the migration logic will be wrapped with a DB transaction.

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

CComponent

CDbMigration

Abstract
Package: system\db
Copyright: 2008-2013 Yii Software LLC
License: http://www.yiiframework.com/license/
Author: Qiang Xue <qiang.xue@gmail.com>
Since: 1.1.6
Located at x2engine/framework/db/CDbMigration.php

Methods summary
`public boolean`	# `up( )` This method contains the logic to be executed when applying this migration. Child classes may implement this method to provide actual migration logic. This method contains the logic to be executed when applying this migration. Child classes may implement this method to provide actual migration logic. Returns `boolean` Returning false means, the migration will not be applied.
`public boolean`	# `down( )` This method contains the logic to be executed when removing this migration. Child classes may override this method if the corresponding migrations can be removed. This method contains the logic to be executed when removing this migration. Child classes may override this method if the corresponding migrations can be removed. Returns `boolean` Returning false means, the migration will not be applied.
`public boolean`	# `safeUp( )` This method contains the logic to be executed when applying this migration. This method differs from `CDbMigration::up()` in that the DB logic implemented here will be enclosed within a DB transaction. Child classes may implement this method instead of `CDbMigration::up()` if the DB logic needs to be within a transaction. This method contains the logic to be executed when applying this migration. This method differs from `CDbMigration::up()` in that the DB logic implemented here will be enclosed within a DB transaction. Child classes may implement this method instead of `CDbMigration::up()` if the DB logic needs to be within a transaction. Returns `boolean` Returning false means, the migration will not be applied and the transaction will be rolled back. Since 1.1.7
`public boolean`	# `safeDown( )` This method contains the logic to be executed when removing this migration. This method differs from `CDbMigration::down()` in that the DB logic implemented here will be enclosed within a DB transaction. Child classes may implement this method instead of `CDbMigration::up()` if the DB logic needs to be within a transaction. This method contains the logic to be executed when removing this migration. This method differs from `CDbMigration::down()` in that the DB logic implemented here will be enclosed within a DB transaction. Child classes may implement this method instead of `CDbMigration::up()` if the DB logic needs to be within a transaction. Returns `boolean` Returning false means, the migration will not be applied and the transaction will be rolled back. Since 1.1.7
`public CDbConnection`	# `getDbConnection( )` Returns the currently active database connection. By default, the 'db' application component will be returned and activated. You can call `CDbMigration::setDbConnection()` to switch to a different database connection. Methods such as `CDbMigration::insert()`, `CDbMigration::createTable()` will use this database connection to perform DB queries. Returns the currently active database connection. By default, the 'db' application component will be returned and activated. You can call `CDbMigration::setDbConnection()` to switch to a different database connection. Methods such as `CDbMigration::insert()`, `CDbMigration::createTable()` will use this database connection to perform DB queries. Returns `CDbConnection` the currently active database connection Throws `CException` if "db" application component is not configured
`public`	# `setDbConnection( CDbConnection $db )` Sets the currently active database connection. The database connection will be used by the methods such as `CDbMigration::insert()`, `CDbMigration::createTable()`. Sets the currently active database connection. The database connection will be used by the methods such as `CDbMigration::insert()`, `CDbMigration::createTable()`. Parameters `$db` `CDbConnection` $db the database connection component
`public`	# `execute( string $sql, array $params = array() )` Executes a SQL statement. This method executes the specified SQL statement using dbConnection. Executes a SQL statement. This method executes the specified SQL statement using dbConnection. Parameters `$sql` `string` $sql the SQL statement to be executed `$params` `array` $params input parameters (name=>value) for the SQL execution. See `CDbCommand::execute()` for more details. Since 1.1.7
`public`	# `insert( string $table, array $columns )` Creates and executes an INSERT SQL statement. The method will properly escape the column names, and bind the values to be inserted. Creates and executes an INSERT SQL statement. The method will properly escape the column names, and bind the values to be inserted. Parameters `$table` `string` $table the table that new rows will be inserted into. `$columns` `array` $columns the column data (name=>value) to be inserted into the table.
`public`	# `insertMultiple( string $table, array $data )` Creates and executes an INSERT SQL statement with multiple data. The method will properly escape the column names, and bind the values to be inserted. Creates and executes an INSERT SQL statement with multiple data. The method will properly escape the column names, and bind the values to be inserted. Parameters `$table` `string` $table the table that new rows will be inserted into. `$data` `array` $data an array of various column data (name=>value) to be inserted into the table. Since 1.1.16
`public`	# `update( string $table, array $columns, mixed $conditions = '', array $params = array() )` Creates and executes an UPDATE SQL statement. The method will properly escape the column names and bind the values to be updated. Creates and executes an UPDATE SQL statement. The method will properly escape the column names and bind the values to be updated. Parameters `$table` `string` $table the table to be updated. `$columns` `array` $columns the column data (name=>value) to be updated. `$conditions` `mixed` $conditions the conditions that will be put in the WHERE part. Please refer to `CDbCommand::where()` on how to specify conditions. `$params` `array` $params the parameters to be bound to the query.
`public`	# `delete( string $table, mixed $conditions = '', array $params = array() )` Creates and executes a DELETE SQL statement. Creates and executes a DELETE SQL statement. Parameters `$table` `string` $table the table where the data will be deleted from. `$conditions` `mixed` $conditions the conditions that will be put in the WHERE part. Please refer to `CDbCommand::where()` on how to specify conditions. `$params` `array` $params the parameters to be bound to the query.
`public`	# `createTable( string $table, array $columns, string $options = null )` Builds and executes a SQL statement for creating a new DB table. Builds and executes a SQL statement for creating a new DB table. The columns in the new table should be specified as name-definition pairs (e.g. 'name'=>'string'), where name stands for a column name which will be properly quoted by the method, and definition stands for the column type which can contain an abstract DB type. The getColumnType method will be invoked to convert any abstract type into a physical one. If a column is specified with definition only (e.g. 'PRIMARY KEY (name, type)'), it will be directly inserted into the generated SQL. Parameters `$table` `string` $table the name of the table to be created. The name will be properly quoted by the method. `$columns` `array` $columns the columns (name=>definition) in the new table. `$options` `string` $options additional SQL fragment that will be appended to the generated SQL.
`public`	# `renameTable( string $table, string $newName )` Builds and executes a SQL statement for renaming a DB table. Builds and executes a SQL statement for renaming a DB table. Parameters `$table` `string` $table the table to be renamed. The name will be properly quoted by the method. `$newName` `string` $newName the new table name. The name will be properly quoted by the method.
`public`	# `dropTable( string $table )` Builds and executes a SQL statement for dropping a DB table. Builds and executes a SQL statement for dropping a DB table. Parameters `$table` `string` $table the table to be dropped. The name will be properly quoted by the method.
`public`	# `truncateTable( string $table )` Builds and executes a SQL statement for truncating a DB table. Builds and executes a SQL statement for truncating a DB table. Parameters `$table` `string` $table the table to be truncated. The name will be properly quoted by the method.
`public`	# `addColumn( string $table, string $column, string $type )` Builds and executes a SQL statement for adding a new DB column. Builds and executes a SQL statement for adding a new DB column. Parameters `$table` `string` $table the table that the new column will be added to. The table name will be properly quoted by the method. `$column` `string` $column the name of the new column. The name will be properly quoted by the method. `$type` `string` $type the column type. The 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'.
`public`	# `dropColumn( string $table, string $column )` Builds and executes a SQL statement for dropping a DB column. Builds and executes a SQL statement for dropping a DB column. Parameters `$table` `string` $table the table whose column is to be dropped. The name will be properly quoted by the method. `$column` `string` $column the name of the column to be dropped. The name will be properly quoted by the method.
`public`	# `renameColumn( string $table, string $name, string $newName )` Builds and executes a SQL statement for renaming a column. Builds and executes a SQL statement for renaming a column. Parameters `$table` `string` $table the table whose column is to be renamed. The name will be properly quoted by the method. `$name` `string` $name the old name of the column. The name will be properly quoted by the method. `$newName` `string` $newName the new name of the column. The name will be properly quoted by the method.
`public`	# `alterColumn( string $table, string $column, string $type )` Builds and executes a SQL statement for changing the definition of a column. Builds and executes a SQL statement for changing the definition of a column. Parameters `$table` `string` $table the table whose column is to be changed. The table name will be properly quoted by the method. `$column` `string` $column the name of the column to be changed. The name will be properly quoted by the method. `$type` `string` $type the new column type. The 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'.
`public`	# `addForeignKey( string $name, string $table, string\|array $columns, string $refTable, string\|array $refColumns, string $delete = null, string $update = null )` Builds a SQL statement for adding a foreign key constraint to an existing table. The method will properly quote the table and column names. Builds a SQL statement for adding a foreign key constraint to an existing table. The method will properly quote the table and column names. Parameters `$name` `string` $name the name of the foreign key constraint. `$table` `string` $table the table that the foreign key constraint will be added to. `$columns` `string\|array` $columns the name of the column to that the constraint will be added on. If there are multiple columns, separate them with commas or pass as an array of column names. `$refTable` `string` $refTable the table that the foreign key references to. `$refColumns` `string\|array` $refColumns the name of the column that the foreign key references to. If there are multiple columns, separate them with commas or pass as an array of column names. `$delete` `string` $delete the ON DELETE option. Most DBMS support these options: RESTRICT, CASCADE, NO ACTION, SET DEFAULT, SET NULL `$update` `string` $update the ON UPDATE option. Most DBMS support these options: RESTRICT, CASCADE, NO ACTION, SET DEFAULT, SET NULL
`public`	# `dropForeignKey( string $name, string $table )` Builds a SQL statement for dropping a foreign key constraint. Builds a SQL statement for dropping a foreign key constraint. Parameters `$name` `string` $name the name of the foreign key constraint to be dropped. The name will be properly quoted by the method. `$table` `string` $table the table whose foreign is to be dropped. The name will be properly quoted by the method.
`public`	# `createIndex( string $name, string $table, string\|array $columns, boolean $unique = false )` Builds and executes a SQL statement for creating a new index. Builds and executes a SQL statement for creating a new index. Parameters `$name` `string` $name the name of the index. The name will be properly quoted by the method. `$table` `string` $table the table that the new index will be created for. The table name will be properly quoted by the method. `$columns` `string\|array` $columns the column(s) that should be included in the index. If there are multiple columns, please separate them by commas or pass as an array of column names. Each column name will be properly quoted by the method, unless a parenthesis is found in the name. `$unique` `boolean` $unique whether to add UNIQUE constraint on the created index.
`public`	# `dropIndex( string $name, string $table )` Builds and executes a SQL statement for dropping an index. Builds and executes a SQL statement for dropping an index. Parameters `$name` `string` $name the name of the index to be dropped. The name will be properly quoted by the method. `$table` `string` $table the table whose index is to be dropped. The name will be properly quoted by the method.
`public`	# `refreshTableSchema( string $table )` Refreshed schema cache for a table Refreshed schema cache for a table Parameters `$table` `string` $table name of the table to refresh Since 1.1.9
`public`	# `addPrimaryKey( string $name, string $table, string\|array $columns )` Builds and executes a SQL statement for creating a primary key, supports composite primary keys. Builds and executes a SQL statement for creating a primary key, supports composite primary keys. Parameters `$name` `string` $name name of the primary key constraint to add `$table` `string` $table name of the table to add primary key to `$columns` `string\|array` $columns comma separated string or array of columns that the primary key will consist of. Array value can be passed since 1.1.14. Since 1.1.13
`public`	# `dropPrimaryKey( string $name, string $table )` Builds and executes a SQL statement for removing a primary key, supports composite primary keys. Builds and executes a SQL statement for removing a primary key, supports composite primary keys. Parameters `$name` `string` $name name of the constraint to remove `$table` `string` $table name of the table to remove primary key from Since 1.1.13

Methods inherited from CComponent
`__call(), __get(), __isset(), __set(), __unset(), asa(), attachBehavior(), attachBehaviors(), attachEventHandler(), canGetProperty(), canSetProperty(), detachBehavior(), detachBehaviors(), detachEventHandler(), disableBehavior(), disableBehaviors(), enableBehavior(), enableBehaviors(), evaluateExpression(), getEventHandlers(), hasEvent(), hasEventHandler(), hasProperty(), raiseEvent()`

Magic properties summary
`public CDbConnection`	`$dbConnection`	# The currently active database connection. The currently active database connection.

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Class CDbMigration

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