Question

I have a table like this:

CREATE TABLE book_info (
     book_id                 VARCHAR(32)     not null,
     title                   varchar(255)    not null,
     author                  varchar(255)    not null,
     folder_path         varchar(255)    not null,
     primary key(book_id)
);

And i insert this data on it:

insert into book_info values('BOOK1', 'APUE', 'Richard Stevens', '/home/user1/unix_programming_books');
insert into book_info values('BOOK2', 'Unix Network programming', 'Richard Stevens', '/home/user1/unix_programming_books');
insert into book_info values('BOOK3', 'Core Python Applications Programming', 'Wesley J. Chun', '/home/user1/python_programming_books');

I’m trying to update this table using Oracle PRO*C, but i can’t! below is my code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

EXEC SQL INCLUDE SQLCA;
EXEC SQL INCLUDE ORACA;

#define USER_LEN                        10                          
#define PASS_LEN                        10                          

VARCHAR user[USER_LEN];
VARCHAR pass[PASS_LEN];

#define STRCPY_TO_ORA(dest, source)\
        dest.len = strlen(source);\
        strcpy((char *)dest.arr, (const char *)source)

#define STRCPY_FROM_ORA(dest, source)\
        source.arr[source.len] = 0;\
        strcpy((char *)dest,(const char *)source.arr)

/* Connecting to the database */
int db_connection(char *db_user, char *db_pass)
{
        strncpy((char *) user.arr, db_user, USER_LEN);
        user.len = strlen((char *) user.arr);
        strncpy((char *) pass.arr, db_pass, PASS_LEN);
        pass.len = strlen((char *) pass.arr);

    EXEC SQL CONNECT :user IDENTIFIED BY :pass;
        if (sqlca.sqlcode != 0)
        {
        fprintf(stdout, "Connection failed:%s\n", sqlca.sqlerrm.sqlerrmc);
                return(sqlca.sqlcode);
        }
    fprintf(stdout, "Connected to ORACLE as user:%s\n", user.arr);
        return (sqlca.sqlcode);
}

int book_not_found_function(char *path)
{
    fprintf(stdout, "%s\n", __FUNCTION__);
}

int path_update_success_function(char *book_id, char *new_path)
{
    fprintf(stdout, "Update book %s path to %s\n", book_id, new_path);
}

void other_function(void)
{
    fprintf(stdout, "%s\n", __FUNCTION__);  
}

/* Updating books path */
int books_path_updating(char *old_path, char *new_path) 
{
    char book_id_string[32];
        EXEC SQL BEGIN DECLARE SECTION;
        varchar sql_old_path[255];
        varchar sql_new_path[255];
    varchar sql_book_id[32];
        EXEC SQL END DECLARE SECTION;

        STRCPY_TO_ORA(sql_old_path, old_path);
        STRCPY_TO_ORA(sql_new_path, new_path);

    /* Declare a cursor for the FETCH statement. */
    EXEC SQL DECLARE books_cursor CURSOR FOR
    SELECT BOOK_ID
        FROM BOOK_INFO 
        WHERE FOLDER_PATH = :sql_old_path;

    if (sqlca.sqlcode != 0)
    {
            fprintf(stdout, "Declare cursor failed\n");
        fprintf(stdout, "Oracle error %s\n", sqlca.sqlerrm.sqlerrmc);
            return(sqlca.sqlcode);
    }

    EXEC SQL OPEN books_cursor;

    if (sqlca.sqlcode != 0)
    {
            fprintf(stdout, "Open cursor failed\n");
        fprintf(stdout, "Oracle error %s\n", sqlca.sqlerrm.sqlerrmc);
            return(sqlca.sqlcode);
    }

    for ( ;; )
    {
        //EXEC SQL WHENEVER NOT FOUND DO break; // I used it but still nothing
        //EXEC SQL WHENEVER NOT FOUND GOTO not_found; // I used this too
        //EXEC SQL WHENEVER NOT FOUND DO continue; // I used this too

            /* Fetching data */
            EXEC SQL FETCH books_cursor 
            INTO :sql_book_id;
        if (sqlca.sqlcode == 1403)
        {
            fprintf(stdout, "No book found for this folder %s\n", old_path);    
            book_not_found_function(old_path);

            return 0;
        }

            else if (sqlca.sqlcode != 0)
            {
            fprintf(stdout, "Oracle error %s\n", sqlca.sqlerrm.sqlerrmc);
                    EXEC SQL CLOSE books_cursor;
                    return (sqlca.sqlcode);
            }

        else
        {
            STRCPY_FROM_ORA(book_id_string, sql_book_id);
                fprintf(stdout, "BOOK_ID = %s\n", book_id_string);
            /* Updating the path */
            EXEC SQL UPDATE BOOK_INFO
            SET FOLDER_PATH =:sql_new_path
            WHERE BOOK_ID =:sql_book_id;
            if (sqlca.sqlcode != 0)
                {
                fprintf(stdout, "Oracle error %s\n", sqlca.sqlerrm.sqlerrmc);
                        EXEC SQL CLOSE books_cursor;
                        return (sqlca.sqlcode);
                }
            else
            {
                path_update_success_function(book_id_string, new_path); 
            }
        }
    }
    EXEC SQL CLOSE books_cursor;
    other_function();

    EXEC SQL COMMIT WORK RELEASE;   
    return 0;   
}

int main(int argc, char **argv)
{
    db_connection("evariste", "123456");

    books_path_updating("/home/user1/unix_programming_books", "/home/user1/UNIX_PROGRAMMING_BOOKS");
    books_path_updating("/non_existing_path", "/non_existing_path");

    return 0;
}

This program produce the output :

Connected to ORACLE as user:evariste
BOOK_ID = BOOK1
Update book BOOK1 path to /home/user1/UNIX_PROGRAMMING_BOOKS
BOOK_ID = BOOK2
Update book BOOK2 path to /home/user1/UNIX_PROGRAMMING_BOOKS
No book found for this folder /home/user1/unix_programming_books // WHEY THIS?
book_not_found_function // WHY THIS
Declare cursor failed   // WHY THIS 
Oracle error ORA-01403: no data found // WHY THIS

The table is not updated and the functions path_update_success_function and other_function are never executed! Why this?

Thanks for your help.

Answer 1

Connected to ORACLE as user:evariste
BOOK_ID = BOOK1
Update book BOOK1 path to /home/user1/UNIX_PROGRAMMING_BOOKS
BOOK_ID = BOOK2
Update book BOOK2 path to /home/user1/UNIX_PROGRAMMING_BOOKS
No book found for this folder /home/user1/unix_programming_books // WHEY THIS?

You’ve fetched past the end of the resultset. Two rows match the cursor this time, so the first two fetches succeed; the third gets no data. This is expected and you shouldn’t treat this as an error – just break the loop, which will also cause other_function to be called.

book_not_found_function // WHY THIS

Because you treat 1403 as an error. If you want to call this function when there are no matches, you’ll need to count in the loop, and call it afterwards if needed.

Declare cursor failed   // WHY THIS 
Oracle error ORA-01403: no data found // WHY THIS

sqlca.sqlcode seems to still be set from the earlier fetch, so this is misleading.

As far as I can remember you’d normally declare the cursor once in the file, not each time the function is called; not sure if Pro*C just ignores the redefinition. You can look at the generated file to see how it deals with it. You also won’t get a runtime error from this, if it’s wrong it won’t (pre-)compile.

The table is not updated and the functions
path_update_success_function and other_function are never executed!
Why this?

path_update_success is called for the first two fetches, but not for the third which fails, and not for the second path because the function returns due to the apparent declare cursor before it gets near it. other_function isn’t called because for both calls you return from the function before you can reach it. Similarly the table seems to not be updated because you return before you commit. Unlike SQL*Plus, Pro*C doesn’t automatically commit on exit, so there is an implicit rollback. Note also that if you did get to the commit, the release disconnects you, so the second time you’d get a not-connected-to-Oracle error. You should decide to commit/rollback once really, probably right at the end of main.

---

Untested modification:

int books_path_updating(char *old_path, char *new_path)
{
    char book_id_string[32];
    int books_found;

    EXEC SQL BEGIN DECLARE SECTION;
        varchar sql_old_path[255];
        varchar sql_new_path[255];
        varchar sql_book_id[32];
    EXEC SQL END DECLARE SECTION;

    STRCPY_TO_ORA(sql_old_path, old_path);
    STRCPY_TO_ORA(sql_new_path, new_path);

    /* Declare a cursor for the FETCH statement */
    EXEC SQL DECLARE books_cursor CURSOR FOR
        SELECT BOOK_ID
        FROM BOOK_INFO
        WHERE FOLDER_PATH = :sql_old_path;

    EXEC SQL OPEN books_cursor;

    if (sqlca.sqlcode != 0)
    {
        fprintf(stdout, "Open cursor failed\n");
    }

    books_found = 0;
    while (sqlca.sqlcode == 0)
    {
        /* Fetching data */
        EXEC SQL FETCH books_cursor
        INTO :sql_book_id;

        if (sqlca.sqlcode != 0)
        {
            break;
        }

        STRCPY_FROM_ORA(book_id_string, sql_book_id);
            fprintf(stdout, "BOOK_ID = %s\n", book_id_string);

        /* Updating the path */
        EXEC SQL UPDATE BOOK_INFO
            SET FOLDER_PATH = :sql_new_path
            WHERE BOOK_ID = :sql_book_id;

        if (sqlca.sqlcode != 0)
        {
            break;
        }

        /* Track how many books we found, though we only really care later that
         * this is non-zero */
        books_found++;

        path_update_success_function(book_id_string, new_path);
    }

    EXEC SQL CLOSE books_cursor;

    /* Check for and display error, but ignore 1403 as this just indicates the
     * end of the result set */
    if ((sqlca.sqlcode != 0) && (sqlca.sqlcode != 1403))
    {
        fprintf(stdout, "Oracle error %s\n", sqlca.sqlerrm.sqlerrmc);
        return 1;
    }

    if (books_found == 0)
    {
        fprintf(stdout, "No book found for this folder %s\n", old_path);
        book_not_found_function(old_path);
        return 0;
    }

    other_function();

    return 0;
}

int main(int argc, char **argv)
{
    int rc;

    rc = db_connection("evariste", "123456");

    /* Only do the first path if we didn't get an error connecting */
    if (rc == 0)
    {
        rc == books_path_updating("/home/user1/unix_programming_books",
            "/home/user1/UNIX_PROGRAMMING_BOOKS");
    }

    /* Only do the next path if we didn't get an error from the previous one */
    if (rc == 0)
    {
        rc = books_path_updating("/non_existing_path",
            "/non_existing_path");
    }

    /* Decide whether to rollback or commit; this assumes you don't want to
     * keep any changes if there are any errors */
    if (rc != 0)
    {
        EXEC SQL ROLLBACK WORK RELEASE;
        return 1;
    }

    EXEC SQL COMMIT WORK RELEASE;
    return 0;
}