librusql-voorbeeldcode voor in libvreemd

foo.cpp

std::string url = "unix:///tmp/mysql.sock";
std::string user = "root";
std::string pass = "";
std::string database = "foo";

rusql::connection c;

try {
  c = rusql::connection(url, user, pass, database);
} catch(rusql::sql_connection_error &e) {
  std::cerr << "Database connection error: " << e.what() << std::endl;
  return;
}

//// STANDARD USE
try {
  rusql::statement s = c.prepare("SELECT * FROM info WHERE id=?");
  rusql::resultset rs = s.execute(6);
  for(auto it = rs.begin(); it != rs.end(); ++it) {
    std::cout << "Row from the info table: " << *it << std::endl;
  }
} catch(rusql::sql_statement_error &e) {
  std::cerr << "Statement error: " << e.what() << std::endl;
}

///// TABLE LOCKING ////
// when tables are locked, only those tables may be used. When the rusql::lock is destructed,
// an UNLOCK TABLES is done, so all tables can be used again.
try {
  
  rusql::lock tables = c.lock_tables({"read" => ["info"], "write" => ["foo", "bar"]});
  rusql::statement read = c.prepare("SELECT * FROM info WHERE id=?");
  rusql::statement write = c.prepare("INSERT INTO foo SET value=? WHERE info_id=?")
  rusql::resultset rs = read.execute(5);
  
  for(auto it = rs.begin(); it != rs.end(); ++it) {
    std::string info_value = it->get("value");
    int info_id = it->get("id");
    try {
      write.execute(info_value, info_id);
    } catch(rusql::sql_statement_error &e) {
      std::cerr << "Foo write error: " << e.what() << std::endl;
    }
  }
  
} catch(rusql::sql_statement_error &e) {
  std::cerr << "Info read error: " << e.what() << std::endl;
}

///// TRANSACTIONS /////
// 1 to 1 ratio between two tables; we want to remove a row from both tables
// without invalidating the database schema. Therefore, use transactions and
// finally do an atomic commit.
try {
  rusql::transaction t = c.start_transaction();
  rusql::statement a = c.prepare("DELETE FROM a WHERE id=?");
  rusql::statement b = c.prepare("DELETE FROM b WHERE id=?");
  rusql::statement s = c.prepare("SELECT id FROM a_and_b WHERE years > 85");
  rusql::resultset rs = s.execute();
  for(auto it = rs.begin(); it != rs.end(); ++it) {
    a.execute(it->get("id"));
    b.execute(it->get("id"));
  }
  t.commit();
} catch(rusql::sql_statement_error &e) {
  std::cerr << "Transaction aborted because of error: " << e.what() << std::endl;
}