执行Select语句示例代码

void main()
{
    char szDSN[] = "XuguDB";
    char szUID[] = "SYSDBA";
    char szAuth[] = "SYSDBA";
    SQLHENV henv = NULL;
    SQLHDBC hdbc = NULL;
    SQLHSTMT hstmt = NULL;
    SQLRETURN ret = 0;
    ret = SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &henv);
    ret = SQLSetEnvAttr(henv, SQL_ATTR_ODBC_VERSION, (SQLPOINTER)SQL_OV_ODBC3, SQL_IS_INTEGER);
    ret = SQLAllocHandle(SQL_HANDLE_DBC, henv, &hdbc);
    ret = SQLConnect(hdbc, (SQLCHAR*)szDSN, SQL_NTS, (SQLCHAR*)szUID, SQL_NTS, (SQLCHAR*)szAuth, SQL_NTS);
    if (ret != SQL_SUCCESS)
    {
        SQLCHAR sqlState[128];
        SQLINTEGER nativeErr;
        SQLCHAR errMsg[256];
        SQLSMALLINT len;
        SQLGetDiagRec(SQL_HANDLE_DBC, hdbc, 1, sqlState, &nativeErr, errMsg, 200, &len);
        printf("Can't connect to server, reason: %s\n", errMsg);
        SQLFreeHandle(SQL_HANDLE_DBC, hdbc);
        SQLFreeHandle(SQL_HANDLE_ENV, henv);
        return;
    }
    printf("Connect successful!\n");
    ret = SQLAllocHandle(SQL_HANDLE_STMT, hdbc, &hstmt);
    char sql[] = "select * from mytable";
    ret = SQLExecDirect(hstmt, (SQLCHAR*)sql, SQL_NTS);
    if (ret != SQL_SUCCESS)
    {
        SQLCHAR sqlState[128];
        SQLINTEGER nativeErr;
        SQLCHAR errMsg[256];
        SQLSMALLINT len;
        SQLGetDiagRec(SQL_HANDLE_STMT, hstmt, 1, sqlState, &nativeErr, errMsg, 200, &len);
        printf("SQLExecDirect failed, reason: %s\n", errMsg);
        SQLFreeHandle(SQL_HANDLE_STMT, hstmt);
        SQLDisconnect(hdbc);
        SQLFreeHandle(SQL_HANDLE_DBC, hdbc);
        SQLFreeHandle(SQL_HANDLE_ENV, henv);
        return;
    }
    SQLLEN cbLen1, cbLen2, cbLen3, cbLen4, cbLen5;
    char col1[30] = { 0 };
    char col2[30] = { 0 };
    char col3[30] = { 0 };
    char col4[30] = { 0 };
    char col5[30] = { 0 };
    SQLBindCol(hstmt, 1, SQL_C_CHAR, col1, 30, &cbLen1);
    SQLBindCol(hstmt, 2, SQL_C_CHAR, col2, 30, &cbLen2);
    SQLBindCol(hstmt, 3, SQL_C_CHAR, col3, 30, &cbLen3);
    SQLBindCol(hstmt, 4, SQL_C_CHAR, col4, 30, &cbLen4);
    SQLBindCol(hstmt, 5, SQL_C_CHAR, col5, 30, &cbLen5);
    while (ret == SQL_SUCCESS)
    {
        ret = SQLFetch(hstmt);
        if (ret == SQL_ERROR || ret == SQL_NO_DATA)
            break;
        printf("%s, %s, %s, %s, %s\n", col1, col2, col3, col4, col5);
    }
    ret = SQLFreeHandle(SQL_HANDLE_STMT, hstmt);

    ret = SQLDisconnect(hdbc);
    ret = SQLFreeHandle(SQL_HANDLE_DBC, hdbc);
    ret = SQLFreeHandle(SQL_HANDLE_ENV, henv);
}