protected function getChangeDefault($tableName, Column $newColumn)
    {
        $constraintName = "DF_{$tableName}_{$newColumn->getName()}";
        $default = $newColumn->getDefault();
        $instructions = new AlterInstructions();

        if ($default === null) {
            $default = 'DEFAULT NULL';
        } else {
            $default = ltrim($this->getDefaultValueDefinition($default));
        }

        if (empty($default)) {
            return $instructions;
        }

        $instructions->addPostStep(sprintf(
            'ALTER TABLE %s ADD CONSTRAINT %s %s FOR %s',
            $this->quoteTableName($tableName),
            $constraintName,
            $default,
            $this->quoteColumnName($newColumn->getName())
        ));

        return $instructions;
    }