fetchData example

protected function setUp(): void
    {
        $this->connection = KernelLifecycleManager::getConnection();
    }

    public function testUpdateDestructiveRemovesColumn(): void
    {
        $existed = $this->columnExists();

        $tableData = null;
        if ($existed) {
            $tableData = $this->fetchData();
        } else {
            $this->addColumn();
        }

        $migration = new Migration1679581138RemoveAssociationFields();
        $migration->updateDestructive($this->connection);
        $migration->updateDestructive($this->connection);

        static::assertFalse($this->columnExists());

        if ($existed) {