我正在教自己Pro * C并且有一个程序通过光标在数据库中记录（据说），并编译并运行。问题是，当变量打印时（使用光标读入的那些），我得到内存中的垃圾。
我尝试用几种不同的方式拆分 sql exec 语句，但这没有帮助。还尝试在不同的地方打开和关闭sql，也无济于事。我真的在一个漫长的调试过程结束时，我很确定在这一点上我犯了一个非常新手的错误。如果这里的任何Oracle程序员都不介意花一点时间，我真的想要一些关于如何回到正轨的反馈。
它应该打印：
Enter a Guest_ID(type 0 to terminate)>>
1
Charge Summary for: Firstname Lastname Guest-ID: 1
Sales_Item: 1 – Room (Taxable)
Hotel-Id Hotel-Name Trans-Date Quantity Unit-Price Extended-Price
Hotel-Id Hotel-Name Trans-Date Quantity Unit-Price Extended-Price
Hotel-Id Hotel-Name Trans-Date Quantity Unit-Price Extended-Price
Sales Item Total Quantity Extended-Price
它实际打印：
Enter a Guest_ID(type 0 to terminate)>>
3
Charge Summary for: l▒ Guest_ID: 3
我觉得我完全弄乱了光标，但我无法准确指出问题所在，因为我仍然习惯于如何在Pro * C中声明和使用变量。此外，C程序通常是经过调试的，但这是在远程服务器上运行的，调试非常有限，甚至没有dbx命令。
代码：
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
exec sql include sqlca;
// OK - Here we GO
void main()
{
// First, create all the variables that we will need to communicate between
// the "C" program and the database
exec sql begin declare section;
//VARCHAR sLastName[51], sFirstName[51], sHotelName[51], sCheckInDate[12], sRoom[11];
VARCHAR sLastName[51], sFirstName[51], sHotelName[51], sTransDate[11];
//int nDays, nGuest_ID, nCount;
int nGuest_ID, nQuantity, nUnitPrice, nCount, nHotelID, nItemID;
//VARCHAR sInCity[11];
VARCHAR sItemName[31], sTaxable[11];
VARCHAR sUserID[21], sPassword[21];
exec sql end declare section;
// Now define the cursor we will use to get all of the charges that the guest incurred at all hotels
exec sql declare dbGuest cursor for
Select G.Guest_ID, G.Last_Name, G.First_Name, C.Item_ID, C.Item_Name, C.Quantity, C.Unit_Price, C.Trans_Date, H.Hotel_Name, H.Hotel_ID, SI.Taxable
From Hotel H, Charge C, Stay S, Guest G, Sales_Item SI Where
C.Stay_ID=S.Stay_ID And H.Hotel_ID=S.Hotel_ID And G.Guest_ID=S.Guest_ID
And SI.Item_ID=C.Item_ID
Group By S.Guest_ID;
// Set up the user-id and password to access my database
// Because we are using the local database on this server
// we don't need to use any database location or SID
strcpy(sUserID.arr,"myuserid");
strcpy(sPassword.arr,"mypassword");
sUserID.len=strlen(sUserID.arr);
sPassword.len=strlen(sPassword.arr);
exec sql connect :sUserID identified by :sPassword;
// sqlca.sqlcode is a variable that is set based on the last command sent in to the database
// a value anything other than zero for what we just did (connect to the database) indicates
// a error.
if(sqlca.sqlcode !=0)
{
//printf("Sorry, cannot connect to server, pgm aborted %s\n",sqlca.sqlcode); //correction 2/5/14
printf("Sorry, cannot connect to server, pgm aborted %d\n",sqlca.sqlcode); //change to %d
exit(1);
}
//we made it here, so we were able to open the database correctly
exec sql SELECT COUNT(*) INTO :nCount FROM Guest;
printf ("There are %d Guests.\n",nCount);
for(;;){
// Read in through stdio the Guest we want to query, then set it up do we can use it
printf("Enter a Guest_ID(type 0 to terminate)>>\n");
scanf("%d",&nGuest_ID);
//Guest_ID.len= strlen(Guest_ID.arr);
if(nGuest_ID==0)
{
printf("BYE\n");
exit(0);
}
printf("%s %s %s %s %d\n","Charge Summary for:", sFirstName.arr, sLastName.arr, " Guest_ID:", nGuest_ID);
//printf("I do not work yet (type exit to terminate)>>\n");
// Open our cursor and begin reading records
exec sql open dbGuest;
for(;;)
{
//exec sql fetch dbGuest into :nGuest_ID, :sLastName, :sFirstName, :sHotelName, :sCheckInDate, :nDays, :sRoom;
exec sql fetch dbGuest into :sLastName, :sFirstName, :nItemID, :sItemName, :nQuantity, :nUnitPrice, :sTransDate, :sHotelName, :nHotelID;
if(sqlca.sqlcode !=0) // If anything went wrong or we read past eof, stop the loop
{
break;
}
printf("%s %s %s %s %d\n","Charge Summary for:", sFirstName.arr, sLastName.arr, " Guest_ID:", nGuest_ID);
// Do the crazy stuff to end the C-Strings
sLastName.arr[sLastName.len] = 0;
sFirstName.arr[sFirstName.len] = 0;
sItemName.arr[sItemName.len] = 0;
sTransDate.arr[sTransDate.len] = 0;
sHotelName.arr[sHotelName.len] = 0;
// Print out the information for this guest
printf("%s %d %s %s \n", "Sales_Item: ", nItemID, " - ", sItemName.arr);
printf("%d %s %s %d %d \n", nHotelID, " ", sHotelName.arr, " ",sTransDate.arr, " ", nQuantity, " ", nUnitPrice);
}
// close the cursor and end the program
exec sql close dbGuest ;
}
exit(0);
}
通常情况下，C程序会在调试器中运行，但这是Pro C而且我对整个Oracle Pro C调试事件感到很遗憾（因为它在远程数据库上运行）。
通过这些但没有帮助：
Strange behaviours with oracle nested cursors
Oracle ProC INSERT INTO VALUES ( (select ...) )
Oracle Pro*C updating table with cursor failed
我被告知应该以不同方式声明VARCHAR变量，但其他方式似乎会抛出错误。
答案 0 :(得分：1)
即使在将值提取到sFirstName之前，也要打印它们。首先，因为您没有初始化它，它会打印 garbage 值。此外，如果您觉得游标提取被中断，在* break * ing LOOP之前，请使用sqlca的sqlerrm来打印错误消息。与sqlca.sqlerrm.sqlerrmc
然后，您的OPEN CURSOR调用将失败，因为查询存在语法错误。
因此，您需要修改光标如下，或者正确修改查询。
我们必须在继续之前检查OPEN cursor的状态，否则FETCH将再次失败，结果可能无法预测。因此，请在每次sqlca.sqlcode来电后查看EXEC SQL。
此外，我们需要处理NULL，如果未使用Indicator variables，我们可以在查询中使用NVL()
exec sql declare dbGuest cursor for
Select G.Guest_ID,
G.Last_Name,
G.First_Name,
C.Item_ID,
C.Item_Name,
C.Quantity,
C.Unit_Price,
C.Trans_Date,
H.Hotel_Name,
H.Hotel_ID,
SI.Taxable
From Hotel H, Charge C, Stay S, Guest G, Sales_Item SI
Where C.Stay_ID=S.Stay_ID
And H.Hotel_ID=S.Hotel_ID
And G.Guest_ID=S.Guest_ID
And SI.Item_ID=C.Item_ID;
非聚合列只能用于聚合函数。因此，请删除分组或将MAX()添加到其他列。
将以下内容添加到声明中
int temp_sales_id = -999;
int first_iter = 1;
int total_nQuantity = 0;
float total_nUnitPrice = 0.0;
然后，
exec sql open dbGuest;
/* Lets check the status of the OPEN statement before proceeding , else exceptions would be suppressed */
if(sqlca.sqlcode !=0) // If anything went wrong or we read past eof, stop the loop
{
printf("Error while opening Cursor <%d><%s>\n",sqlca.sqlcode,sqlca.sqlerrm.sqlerrmc);
break;
}
for(;;)
{
//exec sql fetch dbGuest into :nGuest_ID, :sLastName, :sFirstName, :sHotelName, :sCheckInDate, :nDays, :sRoom;
exec sql fetch dbGuest into :sLastName, :sFirstName, :nItemID, :sItemName, :nQuantity, :nUnitPrice, :sTransDate, :sHotelName, :nHotelID;
/* Check for No DATA FOUND */
if(sqlca.sqlcode == 100 || sqlca.sqlcode == 1403) // If anything went wrong or we read past eof, stop the loop
{
printf("CURSOR is empty after all fetch");
break;
}
/* Check for other errors */
else if(sqlca.sqlcode != 0)
{
printf("Error while fetching from Cursor <%d><%s>\n",sqlca.sqlcode,sqlca.sqlerrm.sqlerrmc);
break;
}
if(first_iter) {
printf("%s %s %s %s %d\n","Charge Summary for:", sFirstName.arr, sLastName.arr, " Guest_ID:", nGuest_ID);
first_iter = 0;
}
// Do the crazy stuff to end the C-Strings
sLastName.arr[sLastName.len] = 0;
sFirstName.arr[sFirstName.len] = 0;
sItemName.arr[sItemName.len] = 0;
sTransDate.arr[sTransDate.len] = 0;
sHotelName.arr[sHotelName.len] = 0;
if(temp_sales_id == -999 || temp_sales_id != nItemID)
{
/* First Item or Sales Item has Changed (next sales id)*/
temp_sales_id = nItemID;
// Print out the information for this guest
printf("%s %d %s %s \n", "Sales_Item: ", nItemID, " - ", sItemName.arr);
printf("%d %s %s %d %d \n", nHotelID, " ", sHotelName.arr, " ",sTransDate.arr, " ", nQuantity, " ", nUnitPrice);
total_nQuantity += nQuantity;
total_nUnitPrice += nUnitPrice;
}
if (temp_sales_id != nItemID) {
/* Printing total for Current Sale id */
/* If you want to Sum all the sale id together take this finally */
printf("Total Quantity <%d> Total Extended Price <%g>\n",total_nQuantity,total_nUnitPrice);
total_nUnitPrice = 0;
total_nQuantity = 0;
}
if(temp_sales_id == -999 || temp_sales_id == nItemID) {
printf("%d %s %s %d %d \n", nHotelID, " ", sHotelName.arr, " ",sTransDate.arr, " ", nQuantity, " ", nUnitPrice);
}
}
// close the cursor and end the program
exec sql close dbGuest ;
答案 1 :(得分：0)
如果您有垃圾值，则可能意味着所获取的数据在数据库中是NULL值。您将需要使用指示器数组来查看什么是NULL。另一种方法是将DB列设置为NOT NULL，以确保您将数据提取到变量中。
我想要检查的第一件事是在SQLPLUS中执行SQL查询，看看你得到了什么结果。如果结果中没有NULL值，则获取的变量不应包含垃圾。
如果结果中有NULL值，请在ProC代码中引入指标数组来处理这种情况。