MySQL- Руководство разработчика




Шаблоны запросов


Другое мощное свойство Mysql++: можно устанавливать шаблоны запросов. Следующий пример показывает, как использовать их. Этот код представляет собой фактический код используемый, чтобы устанавливать и/или сбрасывать типовую базу данных. Этот код может быть найден в файле reset-db.cc. #include <iostream> #include <sqlplus.hh> int main (int argc, char *argv[]) { Connection connection(use_exceptions); try { // the entire main block is one big try block; if (argc == 1) connection.connect(""); else if (argc == 2) connection.connect("",argv[1]); else if (argc == 3) connection.connect("",argv[1],argv[2]); else if (argc <= 4) connection.connect("",argv[1],argv[2],argv[3]); // create a new object and connect based on any (if any) arguments // passed to main(); try { connection.select_db("mysql_cpp_data"); } catch (BadQuery er) { // if it couldn't connect to the database assume that it doesn't exist // and try created it. If that does not work exit with an error. connection.create_db("mysql_cpp_data"); connection.select_db("mysql_cpp_data"); } Query query = connection.query(); // create a new query object try { // ignore any errors here we hope to make this simpler soon query.execute("drop table stock"); } catch (BadQuery er) {} query << "create table stock (item char(20) not null, num smallint," << "weight double, price double, sdate date)"; query.execute(RESET_QUERY); // send the query to create the table and execute it. The // RESET_QUERY tells the query object to reset it self after // execution query << "insert into %5:table values (%q0, %q1, %2, %3, %q4)"; query.parse(); // set up the template query we will use to insert the data. The // parse method call is important as it is what lets the query // know that this is a template and not a literal string query.def["table"] = "stock"; // This is setting the parameter named table to stock. query.execute("Hamburger Buns", 56, 1.25, 1.1, "1998-04-26"); query.execute("Hotdogs' Buns",65, 1.1, 1.1, "1998-04-23"); query.execute("Dinner Roles", 75, 0.95, 0.97, "1998-05-25"); query.execute("White Bread", 87, 1.5, 1.75, "1998-09-04"); // The last parameter "table" is not specified here. Thus // the default value for "table" is used which is "stock". } catch (BadQuery er) { // handle any errors that may come up cerr << "Error: " <<er.error << endl; return -1; } }




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