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
void write(const Block & block) override
    {
        auto blocks = splitBlocks(block, max_batch_rows);
        mysqlxx::Transaction trans(entry);
        try
        {
            for (const Block & batch_data : blocks)
            {
                writeBlockData(batch_data);
            }
            trans.commit();
        }
        catch (...)
        {
            trans.rollback();
            throw;
        }
    }
    void writeBlockData(const Block & block)