sqlbindparameter参数不是用于所有参数- mysql和C++

Question

我在MySQL中定义了下表

INSERT INTO routemaster_log (`EntryDateTime`,`Entry`,`Message`,`EntryType`) VALUES (?,?,?,?);
CREATE TABLE `routemaster_log` (
  `EntryDateTime` datetime NOT NULL DEFAULT CURRENT_TIMESTAMP,
  `Entry` varchar(127) NOT NULL,
  `Message` int(11) NOT NULL DEFAULT '0',
  `EntryType` varchar(20) NOT NULL DEFAULT 'INFORMATION'
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

和下面的C++代码来为它编写记录

void LogEntries::Insert(string_t LogText, string_t LogType, int MessageNumber)
{
    SQLHANDLE   hEnv;
    SQLRETURN   retCode;
    SQLCHAR*    query;
    SQLINTEGER textLength = SQL_NTS;

    // now set the text to be written to char *     
    char* logText = from_string_t(LogText);
    char* logType = from_string_t(LogType);

    std::string SQLQuery("INSERT INTO routemaster_log (`Entry`,`Message`,`EntryType`) VALUES (?,?,?)");

    query = (SQLCHAR *)SQLQuery.c_str();

.
.
.

    // log Text
    retCode = SQLBindParameter(hStmnt, 1, SQL_PARAM_INPUT,
        SQL_C_CHAR, SQL_CHAR, 0, 0,
        logText, sizeof(logText), &textLength);

    if (retCode != SQL_SUCCESS && retCode != SQL_SUCCESS_WITH_INFO) {
        std::cout << "SQL Insert failed binding parameters (LogText)" << std::endl;
    }

    // Message Number
    retCode = SQLBindParameter(hStmnt, 1, SQL_PARAM_INPUT, SQL_C_LONG, SQL_INTEGER, 0, 0, &MessageNumber, 0, NULL);
    if (retCode != SQL_SUCCESS && retCode != SQL_SUCCESS_WITH_INFO) {
        std::cout << "SQL Insert failed binding parameters (Message Number)" << std::endl;
    }

    // Log Type
    retCode = SQLBindParameter(hStmnt, 1, SQL_PARAM_INPUT, 
        SQL_C_CHAR, SQL_CHAR, 0, 0, 
        logType, sizeof(logType), &textLength);

    if (retCode != SQL_SUCCESS && retCode != SQL_SUCCESS_WITH_INFO) {
        std::cout << "SQL Insert failed binding parameters (LogType)" << std::endl;
    }

    retCode = SQLExecDirectA(hStmnt, query, SQL_NTS);
    if (retCode != SQL_SUCCESS && retCode != SQL_SUCCESS_WITH_INFO)
    {
        SQLWCHAR Msg[255], SqlState[6];
        SQLINTEGER NativeError;
        SQLRETURN ret2;
        SQLSMALLINT i, MsgLen;

        i = 1;
        while ((ret2 = SQLGetDiagRec(SQL_HANDLE_STMT, hStmnt, i, SqlState, &NativeError,
            Msg, sizeof(Msg), &MsgLen)) != SQL_NO_DATA) {

            std::cout << Msg << std::endl;

            i++;
        }
        std::cout << "SQL Insert failed writing data to database." << std::endl;
    }
}

一切都很好，直到SQLExecDirectA失败为止，没有将SQLBindParameter用于所有参数错误(在下面的while循环中检索到)。

如果被绑定的参数的数量与“？”的数目不同，我就会想到这一点。在查询中但是它们是相同的。

有人想知道怎么回事吗？

Answer 1

实际上，问题中的代码有两个问题。

( a)对SQLBindParameter的调用在调用SQLPrepareA之前进行

( b)在对SQLBindParameter的调用中，第二个参数给出参数的位置

经修订的守则-其作用如下：

// log Text
retCode = SQLBindParameter(hStmnt, 1, SQL_PARAM_INPUT,
    SQL_C_CHAR, SQL_CHAR, 0, 0,
    logText, sizeof(logText), &textLength);

if (retCode != SQL_SUCCESS && retCode != SQL_SUCCESS_WITH_INFO) {
    std::cout << "SQL Insert failed binding parameters (LogText)" << std::endl;
}

// Message Number
retCode = SQLBindParameter(hStmnt, 2, SQL_PARAM_INPUT, SQL_C_LONG, SQL_INTEGER, 0, 0, &MsgNumber, 0, NULL);
if (retCode != SQL_SUCCESS && retCode != SQL_SUCCESS_WITH_INFO) {
    std::cout << "SQL Insert failed binding parameters (Message Number)" << std::endl;
}

// Log Type
retCode = SQLBindParameter(hStmnt, 3, SQL_PARAM_INPUT, 
    SQL_C_CHAR, SQL_CHAR, 0, 0, 
    logType, sizeof(logType), &textLength);

if (retCode != SQL_SUCCESS && retCode != SQL_SUCCESS_WITH_INFO) {
    std::cout << "SQL Insert failed binding parameters (LogType)" << std::endl;
}

retCode = SQLPrepareA(hStmnt, query, SQL_NTS);
if (retCode != SQL_SUCCESS && retCode != SQL_SUCCESS_WITH_INFO) {
    std::cout << "SQL Insert failed preparing statement" << std::endl;
}


retCode = SQLExecDirectA(hStmnt, query, SQL_NTS);