Create test table:
`CREATE TABLE test (`id` Int32) ENGINE = MySQL('localhost:3306', '', 'test', 'user', 'pass')`

Attempt insert:
`INSERT INTO test VALUES(1)`

CH sending SQL:
`INSERT INTO ``.`test` (`id`) VALUES (1)`

"``." - sending empty database name in generated SQL

However SELECT statement working with empty database name correctrly

P.S.
This can be useful when working with databases such as sphinx
{
        WriteBufferFromOwnString sqlbuf;
        sqlbuf << (storage.replace_query ? "REPLACE" : "INSERT") << " INTO ";
        sqlbuf << backQuoteMySQL(remote_database_name) << "." << backQuoteMySQL(remote_table_name);
        sqlbuf << " (" << dumpNamesWithBackQuote(block) << ") VALUES ";
        auto writer = FormatFactory::instance().getOutputStream("Values", sqlbuf, metadata_snapshot->getSampleBlock(), storage.getContext());
        writer->write(block);
        if (!storage.on_duplicate_clause.empty())
            sqlbuf << " ON DUPLICATE KEY " << storage.on_duplicate_clause;
        sqlbuf << ";";
        auto query = this->entry->query(sqlbuf.str());
        query.execute();
    }
    Blocks splitBlocks(const Block & block, const size_t & max_rows) const