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
#if !defined(ARCADIA_BUILD)
#    include "config_core.h"
#endif
#if USE_MYSQL
#include <Core/Block.h>
#include <Databases/MySQL/FetchTablesColumnsList.h>
#include <DataTypes/convertMySQLDataType.h>
#include <DataTypes/DataTypeString.h>
#include <DataTypes/DataTypesNumber.h>
#include <Formats/MySQLBlockInputStream.h>
#include <IO/WriteBufferFromString.h>
#include <IO/WriteHelpers.h>
#include <IO/Operators.h>
#include <memory>
namespace
{
using namespace DB;
String toQueryStringWithQuote(const std::vector<String> & quote_list)