diff --git a/dbms/include/DB/Core/ErrorCodes.h b/dbms/include/DB/Core/ErrorCodes.h
index bed36b4f74b..c57cef242fe 100644
--- a/dbms/include/DB/Core/ErrorCodes.h
+++ b/dbms/include/DB/Core/ErrorCodes.h
@@ -64,6 +64,7 @@ namespace ErrorCodes
 		STORAGE_DOESNT_ALLOW_PARAMETERS,
 		UNKNOWN_STORAGE,
 		TABLE_ALREADY_EXISTS,
+		TABLE_METADATA_ALREADY_EXISTS,
 	};
 }
 
diff --git a/dbms/include/DB/IO/ReadHelpers.h b/dbms/include/DB/IO/ReadHelpers.h
index 806a7ba380d..ef98cc048e3 100644
--- a/dbms/include/DB/IO/ReadHelpers.h
+++ b/dbms/include/DB/IO/ReadHelpers.h
@@ -12,6 +12,9 @@
 #include <DB/Core/ErrorCodes.h>
 
 #include <DB/IO/ReadBuffer.h>
+#include <DB/IO/VarInt.h>
+
+#define DEFAULT_MAX_STRING_SIZE 0x00FFFFFFULL
 
 
 namespace DB
@@ -65,6 +68,20 @@ inline void readFloatBinary(T & x, ReadBuffer & buf)
 	readBinary(x, buf);
 }
 
+
+inline void readStringBinary(std::string & s, DB::ReadBuffer & buf, size_t MAX_STRING_SIZE = DEFAULT_MAX_STRING_SIZE)
+{
+	size_t size = 0;
+	DB::readVarUInt(size, buf);
+
+	if (size > MAX_STRING_SIZE)
+		throw Poco::Exception("Too large string size.");
+
+	s.resize(size);
+	buf.readStrict(const_cast<char *>(s.data()), size);
+}
+
+
 inline void readChar(char & x, ReadBuffer & buf)
 {
 	if (!buf.eof())
diff --git a/dbms/include/DB/IO/WriteHelpers.h b/dbms/include/DB/IO/WriteHelpers.h
index 99fb659eb88..decb81833f5 100644
--- a/dbms/include/DB/IO/WriteHelpers.h
+++ b/dbms/include/DB/IO/WriteHelpers.h
@@ -13,6 +13,7 @@
 #include <DB/Core/ErrorCodes.h>
 
 #include <DB/IO/WriteBuffer.h>
+#include <DB/IO/VarInt.h>
 
 #define WRITE_HELPERS_DEFAULT_FLOAT_PRECISION 6U
 /// 20 цифр и знак
@@ -52,6 +53,13 @@ inline void writeFloatBinary(T & x, WriteBuffer & buf)
 }
 
 
+inline void writeStringBinary(const std::string & s, DB::WriteBuffer & buf)
+{
+	writeVarUInt(s.size(), buf);
+	buf.write(s.data(), s.size());
+}
+
+
 template <typename T>
 void writeIntText(T x, WriteBuffer & buf)
 {
diff --git a/dbms/include/DB/Interpreters/Context.h b/dbms/include/DB/Interpreters/Context.h
index f3ca44d495c..79c9a2017f8 100644
--- a/dbms/include/DB/Interpreters/Context.h
+++ b/dbms/include/DB/Interpreters/Context.h
@@ -3,6 +3,9 @@
 #include <map>
 #include <set>
 
+#include <Poco/SharedPtr.h>
+#include <Poco/Mutex.h>
+
 #include <DB/Core/NamesAndTypes.h>
 #include <DB/Storages/IStorage.h>
 #include <DB/Functions/IFunction.h>
@@ -12,6 +15,8 @@
 namespace DB
 {
 
+using Poco::SharedPtr;
+
 /// имя функции -> функция
 typedef std::map<String, FunctionPtr> Functions;
 
@@ -27,11 +32,15 @@ typedef std::map<String, Tables> Databases;
 struct Context
 {
 	String path;						/// Путь к директории с данными, со слешем на конце.
-	Databases databases;				/// Список БД и таблиц в них.
+	SharedPtr<Databases> databases;		/// Список БД и таблиц в них.
 	String current_database;			/// Текущая БД.
-	Functions functions;				/// Обычные функции.
+	SharedPtr<Functions> functions;		/// Обычные функции.
 	DataTypeFactory data_type_factory;	/// Типы данных.
 	NamesAndTypes columns;				/// Столбцы текущей обрабатываемой таблицы.
+
+	SharedPtr<Poco::FastMutex> mutex;	/// Для доступа и модификации разделяемых объектов.
+
+	Context() : databases(new Databases), functions(new Functions), mutex(new Poco::FastMutex) {}
 };
 
 
diff --git a/dbms/include/DB/Parsers/ASTCreateQuery.h b/dbms/include/DB/Parsers/ASTCreateQuery.h
index 056603d38e3..058d56093d7 100644
--- a/dbms/include/DB/Parsers/ASTCreateQuery.h
+++ b/dbms/include/DB/Parsers/ASTCreateQuery.h
@@ -14,6 +14,7 @@ class ASTCreateQuery : public IAST
 {
 public:
 	bool attach;	/// Запрос ATTACH TABLE, а не CREATE TABLE.
+	bool if_not_exists;
 	String name;
 	ASTPtr columns;
 	ASTPtr storage;
diff --git a/dbms/include/DB/Parsers/ParserCreateQuery.h b/dbms/include/DB/Parsers/ParserCreateQuery.h
index d31b6ff9f9e..524adb0849f 100644
--- a/dbms/include/DB/Parsers/ParserCreateQuery.h
+++ b/dbms/include/DB/Parsers/ParserCreateQuery.h
@@ -28,7 +28,7 @@ protected:
 
 
 /** Запрос типа такого:
-  * CREATE TABLE name
+  * CREATE|ATTACH TABLE [IF NOT EXISTS] name
   * (
   * 	name1 type1,
   * 	name2 type2,
diff --git a/dbms/include/DB/Storages/IStorage.h b/dbms/include/DB/Storages/IStorage.h
index a6a12537baa..45cad9d4e87 100644
--- a/dbms/include/DB/Storages/IStorage.h
+++ b/dbms/include/DB/Storages/IStorage.h
@@ -49,7 +49,7 @@ public:
 		ASTPtr query,
 		size_t max_block_size = DEFAULT_BLOCK_SIZE)
 	{
-		throw Exception("Method read() is not supported by storage " + getName());
+		throw Exception("Method read() is not supported by storage " + getName(), ErrorCodes::NOT_IMPLEMENTED);
 	}
 
 	/** Пишет данные в таблицу.
@@ -59,7 +59,22 @@ public:
 	virtual SharedPtr<IBlockOutputStream> write(
 		ASTPtr query)
 	{
-		throw Exception("Method write() is not supported by storage " + getName());
+		throw Exception("Method write() is not supported by storage " + getName(), ErrorCodes::NOT_IMPLEMENTED);
+	}
+
+	/** Удалить данные таблицы.
+	  */
+	virtual void drop()
+	{
+		throw Exception("Method drop() is not supported by storage " + getName(), ErrorCodes::NOT_IMPLEMENTED);
+	}
+
+	/** ALTER таблицы в виде изменения столбцов, не затрагивающий изменение Storage или его параметров.
+	  * (ALTER, затрагивающий изменение движка, делается внешним кодом, путём копирования данных.)
+	  */
+	virtual void alter(SharedPtr<NamesAndTypes> columns)
+	{
+		throw Exception("Method alter() is not supported by storage " + getName(), ErrorCodes::NOT_IMPLEMENTED);
 	}
 
 	virtual ~IStorage() {}
diff --git a/dbms/src/DataStreams/tests/expression_stream.cpp b/dbms/src/DataStreams/tests/expression_stream.cpp
index 6b72caf2cb8..4119c335fd1 100644
--- a/dbms/src/DataStreams/tests/expression_stream.cpp
+++ b/dbms/src/DataStreams/tests/expression_stream.cpp
@@ -48,9 +48,9 @@ int main(int argc, char ** argv)
 
 		DB::Context context;
 		context.columns["number"] = new DB::DataTypeUInt64;
-		context.functions["plus"] = new DB::FunctionPlus;
-		context.functions["multiply"] = new DB::FunctionMultiply;
-		context.functions["divide"] = new DB::FunctionDivideFloating;
+		(*context.functions)["plus"] = new DB::FunctionPlus;
+		(*context.functions)["multiply"] = new DB::FunctionMultiply;
+		(*context.functions)["divide"] = new DB::FunctionDivideFloating;
 
 		Poco::SharedPtr<DB::Expression> expression = new DB::Expression(ast, context);
 
diff --git a/dbms/src/Interpreters/Expression.cpp b/dbms/src/Interpreters/Expression.cpp
index bbad0353531..3b557b62ec1 100644
--- a/dbms/src/Interpreters/Expression.cpp
+++ b/dbms/src/Interpreters/Expression.cpp
@@ -15,8 +15,8 @@ void Expression::addSemantic(ASTPtr ast)
 {
 	if (ASTFunction * node = dynamic_cast<ASTFunction *>(&*ast))
 	{
-		Functions::const_iterator it = context.functions.find(node->name);
-		if (it == context.functions.end())
+		Functions::const_iterator it = context.functions->find(node->name);
+		if (it == context.functions->end())
 			throw Exception("Unknown function " + node->name, ErrorCodes::UNKNOWN_FUNCTION);
 
 		node->function = it->second;
diff --git a/dbms/src/Interpreters/InterpreterCreateQuery.cpp b/dbms/src/Interpreters/InterpreterCreateQuery.cpp
index 1f53ae5be58..5b0fbe89a94 100644
--- a/dbms/src/Interpreters/InterpreterCreateQuery.cpp
+++ b/dbms/src/Interpreters/InterpreterCreateQuery.cpp
@@ -18,12 +18,21 @@ StoragePtr InterpreterCreateQuery::execute(ASTPtr query, Context & context)
 	String database_name = context.current_database;
 	String table_name = create.name;
 	SharedPtr<NamesAndTypes> columns = new NamesAndTypes;
-	String data_path = context.path + "data/" + database_name + "/" + table_name + "/";	/// TODO: эскейпинг
+	String data_path = context.path + "data/" + database_name + "/";	/// TODO: эскейпинг
 	String metadata_path = context.path + "metadata/" + database_name + "/" + table_name + ".sql";
 
-	if (context.databases[database_name].end() != context.databases[database_name].find(table_name))
-		throw Exception("Table " + database_name + "." + table_name + " already exists.", ErrorCodes::TABLE_ALREADY_EXISTS);
-
+	{
+		Poco::ScopedLock<Poco::FastMutex> lock(*context.mutex);
+		
+		if ((*context.databases)[database_name].end() != (*context.databases)[database_name].find(table_name))
+		{
+			if (create.if_not_exists)
+				return (*context.databases)[database_name][table_name];
+			else
+				throw Exception("Table " + database_name + "." + table_name + " already exists.", ErrorCodes::TABLE_ALREADY_EXISTS);
+		}
+	}
+	
 	ASTExpressionList & columns_list = dynamic_cast<ASTExpressionList &>(*create.columns);
 	for (ASTs::iterator it = columns_list.children.begin(); it != columns_list.children.end(); ++it)
 	{
@@ -57,18 +66,21 @@ StoragePtr InterpreterCreateQuery::execute(ASTPtr query, Context & context)
 	else
 		throw Exception("Unknown storage " + storage_str, ErrorCodes::UNKNOWN_STORAGE);
 
-	if (!create.attach)
+	/// Проверка наличия метаданных таблицы на диске и создание метаданных
+
+	if (Poco::File(metadata_path).exists())
+		throw Exception("Metadata for table " + database_name + "." + table_name + " already exists.",
+			ErrorCodes::TABLE_METADATA_ALREADY_EXISTS);
+
+	Poco::FileOutputStream metadata_file(metadata_path);
+	metadata_file << String(create.range.first, create.range.second - create.range.first) << std::endl;
+
 	{
-		/// Проверка наличия метаданных таблицы на диске и создание метаданных
+		Poco::ScopedLock<Poco::FastMutex> lock(*context.mutex);
 
-		if (Poco::File(metadata_path).exists())
-			throw Exception("Table " + database_name + "." + table_name + " already exists.", ErrorCodes::TABLE_ALREADY_EXISTS);
-
-		Poco::FileOutputStream metadata_file(metadata_path);
-		metadata_file << String(create.range.first, create.range.second - create.range.first) << std::endl;
+		(*context.databases)[database_name][table_name] = res;
 	}
-
-	context.databases[database_name][table_name] = res;
+	
 	return res;
 }
 
diff --git a/dbms/src/Interpreters/tests/create_query.cpp b/dbms/src/Interpreters/tests/create_query.cpp
index 037739d0bfd..76507aeb4d6 100644
--- a/dbms/src/Interpreters/tests/create_query.cpp
+++ b/dbms/src/Interpreters/tests/create_query.cpp
@@ -13,7 +13,7 @@ int main(int argc, char ** argv)
 	{
 		DB::ParserCreateQuery parser;
 		DB::ASTPtr ast;
-		std::string input = "CREATE TABLE hits (\n"
+		std::string input = "CREATE TABLE IF NOT EXISTS hits (\n"
 			"WatchID				UInt64,\n"
 			"JavaEnable 			UInt8,\n"
 			"Title 					String,\n"
@@ -95,7 +95,7 @@ int main(int argc, char ** argv)
 		DB::Context context;
 
 		context.path = "./";
-		context.databases["test"];
+		(*context.databases)["test"];
 		context.current_database = "test";
 
 		DB::InterpreterCreateQuery interpreter;
diff --git a/dbms/src/Interpreters/tests/expression.cpp b/dbms/src/Interpreters/tests/expression.cpp
index 59e460b3e71..f9c039f1c9d 100644
--- a/dbms/src/Interpreters/tests/expression.cpp
+++ b/dbms/src/Interpreters/tests/expression.cpp
@@ -100,8 +100,8 @@ int main(int argc, char ** argv)
 
 		DB::Context context;
 		context.columns["x"] = new DB::DataTypeInt16;
-		context.functions["plus"] = new DB::FunctionPlus;
-		context.functions["multiply"] = new DB::FunctionMultiply;
+		(*context.functions)["plus"] = new DB::FunctionPlus;
+		(*context.functions)["multiply"] = new DB::FunctionMultiply;
 
 		DB::Expression expression(ast, context);
 
diff --git a/dbms/src/Parsers/ParserCreateQuery.cpp b/dbms/src/Parsers/ParserCreateQuery.cpp
index 0f4b041c2a2..51971328f74 100644
--- a/dbms/src/Parsers/ParserCreateQuery.cpp
+++ b/dbms/src/Parsers/ParserCreateQuery.cpp
@@ -78,6 +78,9 @@ bool ParserCreateQuery::parseImpl(Pos & pos, Pos end, ASTPtr & node, String & ex
 	ParserString s_rparen(")");
 	ParserString s_engine("ENGINE", true);
 	ParserString s_eq("=");
+	ParserString s_if("IF", true);
+	ParserString s_not("NOT", true);
+	ParserString s_exists("EXISTS", true);
 	ParserIdentifier name_p;
 	ParserList columns_p(new ParserNameTypePair, new ParserString(","), false);
 	ParserIdentifierWithOptionalParameters storage_p;
@@ -86,6 +89,7 @@ bool ParserCreateQuery::parseImpl(Pos & pos, Pos end, ASTPtr & node, String & ex
 	ASTPtr columns;
 	ASTPtr storage;
 	bool attach = false;
+	bool if_not_exists = false;
 
 	ws.ignore(pos, end);
 
@@ -97,12 +101,16 @@ bool ParserCreateQuery::parseImpl(Pos & pos, Pos end, ASTPtr & node, String & ex
 			return false;
 	}
 
-	ws.ignore(pos, end);
-
-	if (!s_table.ignore(pos, end, expected))
+	if (!ws.ignore(pos, end) || !s_table.ignore(pos, end, expected) || !ws.ignore(pos, end))
 		return false;
 
-	ws.ignore(pos, end);
+	if (s_if.ignore(pos, end, expected)
+		&& ws.ignore(pos, end)
+		&& s_not.ignore(pos, end, expected)
+		&& ws.ignore(pos, end)
+		&& s_exists.ignore(pos, end, expected)
+		&& ws.ignore(pos, end))
+		if_not_exists = true;
 
 	if (!name_p.parse(pos, end, name, expected))
 		return false;
@@ -141,6 +149,7 @@ bool ParserCreateQuery::parseImpl(Pos & pos, Pos end, ASTPtr & node, String & ex
 	node = query;
 
 	query->attach = attach;
+	query->if_not_exists = if_not_exists;
 	query->name = dynamic_cast<ASTIdentifier &>(*name).name;
 	query->columns = columns;
 	query->storage = storage;