Question

I’m currently passing a multidimensional char array to my MySQL function. cmd contains the command and resultSet[2][50] is my array.

How can I make this more dynamic so that I’m able to retrieve as many items as I want?

int
selectDB(char * cmd, char resultSet[2][50])
{
    MYSQL *conn;
    MYSQL_RES *result;
    MYSQL_ROW row;
    int i;
    char *c1;

    conn = mysql_init(NULL);

    if (conn == NULL) {
        printf("Error %u: %s\n", mysql_errno(conn), mysql_error(conn));
        exit(1);
    }

    if (mysql_real_connect(conn, "localhost", "root",
    "mypassword", "myDBName", 0, NULL, 0) == NULL)
    {
        printf("Error %u: %s\n", mysql_errno(conn), mysql_error(conn));
        exit(1);    
    }

    if (mysql_query(conn, cmd)) 
    {
        printf("Error %u: %s\n", mysql_errno(conn), mysql_error(conn));
        exit(1);
    }

    if (!(result = mysql_store_result(conn)))
   {
        printf("Error %u: %s\n", mysql_errno(conn), mysql_error(conn));
        exit(1);
    }   
    while((row = mysql_fetch_row(result))) {
        for (i=0 ; i < mysql_num_fields(result); i++)               
                {
                snprintf(resultSet[i], 999, "%s", row[i]);      
                }

    }

    if (!mysql_eof(result))
    {
        printf("Error %u: %s\n", mysql_errno(conn), mysql_error(conn));
        exit(1);
    }

   mysql_free_result(result);   
    mysql_close(conn);
    return 0;
}

Answer 1

You could accept a triple pointer as an argument like this and an int, that will tell the size of the array

int selectDB( char* cmd, char*** resultSet, int* m, int* n )
{
    // allocate two dimentional array with any size you want, using malloc
    // store the size into m and n
    // do stuff with resultSet
    // watch out when using snprintf - check if i is smaller
    // than the size of the array. If so - just use snprintf
    // otherwise, you'll need to allocate some larger memory, 
    // and copy "move" the current records into the new location
    // then free the old memory, etc.
    // 
    // return
}

This way you’ll know the size of the array, but you’ll need to take care of freeing the memory, allocated for resultSet.