--- a/bash-completion.sh	Fri Dec 13 22:19:41 2019 +0100
+++ b/bash-completion.sh	Sat Dec 14 14:00:36 2019 +0100
@@ -21,9 +21,16 @@
 	w1=${COMP_WORDS[COMP_CWORD-1]}
 	w2=${COMP_WORDS[COMP_CWORD-2]}
 
+	DATA_TYPE=(
+		"string"
+		"integer"
+		"boolean"
+	)
 
 	if   [[ "$w1" == "--relation"      && "x$w0" == "x" ]];    then COMPREPLY=("''")
 	elif [[ "$w2" == "--relation"      && "x$w0" == "x" ]];    then COMPREPLY=('"SELECT * FROM "')
+	elif [[ "$w1" == "--type-cast"     && "x$w0" == "x" ]];    then COMPREPLY=("''")
+	elif [[ "$w2" == "--type-cast"                      ]];    then COMPREPLY=($(compgen -W "${DATA_TYPE[*]}" -- "$w0"))
 	elif [[ "$w1" == "--parameter"     && "x$w0" == "x" ]];    then COMPREPLY=("''")
 	elif [[ "$w1" == "--copy"          && "x$w0" == "x" ]];    then COMPREPLY=("'.+'")
 	elif [[ "$w1" == "--copy-renamed"  && "x$w0" == "x" ]];    then COMPREPLY=("'.+'")
@@ -33,6 +40,7 @@
 	else
 		OPTIONS=(
 			"--relation"
+			"--type-cast"
 			"--parameter"
 			"--copy"
 			"--copy-renamed"

--- a/src/CLIParser.h	Fri Dec 13 22:19:41 2019 +0100
+++ b/src/CLIParser.h	Sat Dec 14 14:00:36 2019 +0100
@@ -48,6 +48,7 @@
 public:
 
 	static const string_t OPTION_RELATION;
+	static const string_t OPTION_TYPE_CAST;
 	static const string_t OPTION_PARAMETER;
 	static const string_t OPTION_COPY;
 	static const string_t OPTION_COPY_RENAMED;
@@ -65,6 +66,11 @@
 				addQuery(c, currentQuery); // previous relation
 				currentQuery.relation = readNext(arguments, i);
 				currentQuery.sql = readNext(arguments, i);
+			} else if (option == OPTION_TYPE_CAST) {
+				TypeCast typeCast;
+				typeCast.name = readNext(arguments, i);
+				typeCast.type = readNext(arguments, i);
+				currentQuery.typeCasts.push_back(typeCast);
 			} else if (option == OPTION_PARAMETER) {
 				Parameter parameter;
 				parameter.value = readNext(arguments, i);
@@ -97,6 +103,7 @@
 // TODO: --type string/integer/boolean (default is string)
 
 const string_t CLIParser::OPTION_RELATION = L"--relation";
+const string_t CLIParser::OPTION_TYPE_CAST = L"--type-cast";
 const string_t CLIParser::OPTION_PARAMETER = L"--parameter";
 const string_t CLIParser::OPTION_COPY = L"--copy";
 const string_t CLIParser::OPTION_COPY_RENAMED = L"--copy-renamed";

--- a/src/Configuration.h	Fri Dec 13 22:19:41 2019 +0100
+++ b/src/Configuration.h	Sat Dec 14 14:00:36 2019 +0100
@@ -30,6 +30,13 @@
 	// TODO: relpipe::writer::TypeId type;
 };
 
+class TypeCast {
+public:
+
+	relpipe::writer::string_t name;
+	relpipe::writer::string_t type;
+};
+
 class Statement {
 public:
 
@@ -46,6 +53,14 @@
 	 * might be also DML or DDL
 	 */
 	relpipe::writer::string_t sql;
+	/**
+	 * Explicitly defined types of particular attributes.
+	 * SQLite uses dynamic typing, so it is often impossible to obtain the proper types from the result set.
+	 */
+	std::vector<TypeCast> typeCasts;
+	/**
+	 * Query parameters
+	 */
 	std::vector<Parameter> parameters;
 };
 

--- a/src/SqlHandler.h	Fri Dec 13 22:19:41 2019 +0100
+++ b/src/SqlHandler.h	Sat Dec 14 14:00:36 2019 +0100
@@ -103,21 +103,25 @@
 		else throw SqlException(L"Unable to get SQLite column name.");
 	}
 
-	relpipe::writer::TypeId getColumType(int columnIndex) {
+	relpipe::writer::TypeId getColumType(int columnIndex, relpipe::writer::TypeId defaultType = relpipe::writer::TypeId::STRING) {
 		const char* type = sqlite3_column_decltype(stmt, columnIndex);
 
 		// TODO: sqlite3_column_decltype returns value only for columns of existing tables, not for dynamic expressions – SQLite uses dynamic types
+		// maybe we could write a function/module that returns result set metadata for given query (before executing it)
+		// or use at least explicit casts in SQL and modify sqlite3_column_decltype() function or add some new one to return such casted type
+		// 
 		// fprintf(stderr, "%d → %s\n", columnIndex, type);
 		// SELECT typeof(1+1); == "integer"
 		// https://www.sqlite.org/c3ref/column_decltype.html – sqlite3_column_decltype
 		// https://www.sqlite.org/c3ref/column_blob.html – sqlite3_column_type
 		// https://www.sqlite.org/datatype3.html – Datatypes In SQLite Version 3
 		// https://dba.stackexchange.com/questions/203220/sqlite-what-is-the-use-of-specifying-data-types
+		// https://www.mail-archive.com/sqlite-users@mailinglists.sqlite.org/msg118093.html
 
 		if (type == nullptr) return relpipe::writer::TypeId::STRING;
 		else if (strcmp(type, "integer") == 0) return relpipe::writer::TypeId::INTEGER;
 		else if (strcmp(type, "text") == 0) return relpipe::writer::TypeId::STRING;
-		else return relpipe::writer::TypeId::STRING;
+		else return defaultType;
 		// TODO: support also other data types
 	}
 
@@ -202,8 +206,13 @@
 		}
 	}
 
+	relpipe::writer::TypeId findType(string_t columnName, int columnIndex, const Statement& statement, std::shared_ptr<PreparedStatement> preparedStatement) {
+		for (TypeCast typeCast : statement.typeCasts) if (typeCast.name == columnName) return relationalWriter->toTypeId(typeCast.type);
+		return preparedStatement->getColumType(columnIndex);
+	}
+
 	void processStatement(const Statement& statement) {
-		std::unique_ptr<PreparedStatement> prepared(connection->prepareStatement(convertor.to_bytes(statement.sql).c_str()));
+		std::shared_ptr<PreparedStatement> prepared(connection->prepareStatement(convertor.to_bytes(statement.sql).c_str()));
 		int columnCount = prepared->getColumnCount();
 		int parameterCount = statement.parameters.size();
 
@@ -212,7 +221,10 @@
 		}
 
 		std::vector<relpipe::writer::AttributeMetadata> metadata;
-		for (int i = 0; i < columnCount; i++) metadata.push_back({convertor.from_bytes(prepared->getColumName(i).c_str()), prepared->getColumType(i)});
+		for (int i = 0; i < columnCount; i++) {
+			string_t columnName = convertor.from_bytes(prepared->getColumName(i).c_str());
+			metadata.push_back({columnName, findType(columnName, i, statement, prepared)});
+		}
 		relationalWriter->startRelation(statement.relation, metadata, true);
 
 		while (prepared->next()) {