Insert.php

<?php

namespace Drupal\Core\Database\Driver\sqlite;

use Drupal\Core\Database\Query\Insert as QueryInsert;

/**
 * SQLite implementation of \Drupal\Core\Database\Query\Insert.
 *
 * We ignore all the default fields and use the clever SQLite syntax:
 *   INSERT INTO table DEFAULT VALUES
 * for degenerated "default only" queries.
 */
class Insert extends QueryInsert {
    public function execute() {
        if (!$this->preExecute()) {
            return NULL;
        }
        if (count($this->insertFields) || !empty($this->fromQuery)) {
            return parent::execute();
        }
        else {
            return $this->connection
                ->query('INSERT INTO {' . $this->table . '} DEFAULT VALUES', [], $this->queryOptions);
        }
    }
    public function __toString() {
        // Create a sanitized comment string to prepend to the query.
        $comments = $this->connection
            ->makeComment($this->comments);
        // Produce as many generic placeholders as necessary.
        $placeholders = [];
        if (!empty($this->insertFields)) {
            $placeholders = array_fill(0, count($this->insertFields), '?');
        }
        // If we're selecting from a SelectQuery, finish building the query and
        // pass it back, as any remaining options are irrelevant.
        if (!empty($this->fromQuery)) {
            $insert_fields_string = $this->insertFields ? ' (' . implode(', ', $this->insertFields) . ') ' : ' ';
            return $comments . 'INSERT INTO {' . $this->table . '}' . $insert_fields_string . $this->fromQuery;
        }
        return $comments . 'INSERT INTO {' . $this->table . '} (' . implode(', ', $this->insertFields) . ') VALUES (' . implode(', ', $placeholders) . ')';
    }

}