c++ - mysql 结果集为空？

Question

编辑

后续问题:mysql resultset is always null

--

resultset 似乎是空的，我确信该表存在，没有抛出 SQLException。它应该打印计数，但实际上没有。

C 数据库 header

class CDatabase
{
    bool verify(string, string);
public:
    sql::Connection *con;
    CDatabase();
    ~CDatabase();
};

CDatabase::CDatabase

con = driver->connect("", "", "");
con->setSchema("");

CDatabase::验证

bool CDatabase::verify(string channel, string hyper_key)
{
    if (!con) return false;
    try
    {
        sql::Statement *stmt;
        sql::ResultSet *res;
        stmt = con->createStatement();
        stmt->execute("SELECT COUNT(*) FROM dark_souls2_widgets");
        res = stmt->getResultSet();
        cout << res->rowsCount();
        delete stmt;
        delete res;
    }
    catch (sql::SQLException &e) {
        cout << "# ERR: SQLException in " << __FILE__;
        cout << "(" << __FUNCTION__ << ") on line »" << __LINE__ << endl;
        cout << "# ERR: " << e.what();
        cout << " (MySQL error code: " << e.getErrorCode();
        cout << ", SQLState: " << e.getSQLState() << " )" << endl;
        return false;
    }
    return false;
}

Answer 1

它不应该显示计数，它应该显示 1，因为这个查询要么失败，要么结果只有一行。如果您想知道表 dark_souls2_widgets 中存在多少行，那么您可以使用

res = stmt->getResultSet();

while (res->next()) {
  cout << res->getInt(1); // getInt(1) returns the first column
}