getAttribute() public method Retrieve a database connection attribute. It is necessary to override PDO's method as some MSSQL PDO driver (e.g. dblib) does not support getting attributes public mixed getAttribute ( $attribute )$attribute integer One of the PDO::ATTR_* constants. return mixed A successful call returns the value of the requested PDO attribute. An unsuccessful call returns null.

commit() public method Commits a transaction. It is necessary to override PDO's method as MSSQL PDO driver does not natively support transactions. public boolean commit ( )return boolean The result of a transaction commit.

beginTransaction() public method Starts a transaction. It is necessary to override PDO's method as MSSQL PDO driver does not natively support transactions. public boolean beginTransaction ( )return boolean The result of a transaction start.

up() public abstract method This method contains the logic to be executed when applying this migration. public abstract 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.

down() public abstract 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. public abstract 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.

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

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.

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.

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. 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.

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. 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 s