Question

The following code fails on QSqlQuery::exec(). When I run the query without the prepared statement argument, it returns the correct results, available as one would expect through QSqlQuery::next()

executedQuery() reports that ":username" was in fact not replaced by the argument, but with a ? (Is it supposed to, since the query did not execute successfully?).

db_ is a QSqlDatabase class variable and isOpen() reports true. The Qt framework verison is 4.7.3.

DBSql::userInfo(const QString &username, 
                QString &passwd, 
                QString &name, 
                UserPriv priv)
{
  QSqlQuery userQuery(db_);
  const QString userStr("SELECT u.id, u.fullname, u.password, p.description \
                        FROM users u INNER JOIN privilege p ON u.privilege_id = p.id \
                      WHERE u.username = :username");
  userQuery.bindValue(":username", username);

  if (!userQuery.prepare(userStr))
    std::cout << "prepare failed" << std::endl;

  if (userQuery.exec()) {
    while (userQuery.next()) {
      userId = userQuery.value(0).toInt();
      name = userQuery.value(1).toString();
      passwd = userQuery.value(2).toString();
      const QString privilegeDesc = userQuery.value(3).toString();
    }
  }
}

Answer 1

You have to call userQuery->prepare(userStr) before userQuery->bindValue(":username", username)