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I am trying to access some names from sqlite3 database and store it to an array of pointer to char using c code

But finally, its assigning the same string repeatedly into all the array of pointers location.

Kindly help me to fix this issue. I tried my level best.. But no improvement. Thanks in advance.

My code:

#include<stdio.h>
#include<stdlib.h>
#include<sqlite3.h>

const char* data = "Callback function called";

sqlite3 *db;
int sql_result;
char *sql;
char *zErrMsg;
int count = 0;

char *store[50];
char **result;

static int callback(void *NotUsed, int argc, char **argv, char **azColName)
{
  static int j = 0;
  int i = 0;
  printf("\n j_value:%d\n",j);
  printf("\n argc: %d", argc);
  for(i = 0; i < argc; i++)
  {
        printf("\n %s = %s", azColName[i], argv[i] ? argv[i] : "NULL"); 
        result[i] = argv[i]; /* Getting database values */
  }

  if(j < count)
  {
     store[j] = result[0];  /* Assigning data to array of pointer */
     printf("\n output[%d]:%s\n",j, store[j]);
     j++;
     if(j == count)
        j = 0;
  }
  for(i = 0;i < count;i++)
  {
     printf("\n Final output[%d]:%s\n",i, store[i]);
  }
  return 0;
}

int open_db() /* Open database */
{

  sql_result = sqlite3_open("test.db", &db);
  if( sql_result ){
  printf( "Error:%s", sqlite3_errmsg(db));
  exit(0);
}else{
 //printf("\nsuccess\n");
}
return 0;

}

int exec_db()  /* Execute SQL statement */
{
   sql_result = sqlite3_exec(db, sql, callback, (void*)data, &zErrMsg);
   if( sql_result != SQLITE_OK ){
   printf( "Error:%s", zErrMsg);
   sqlite3_free(zErrMsg);
 }else{
  //printf("\nsuccess\n");
 }
return 0;

}

int main()
{
  open_db();
  result = (char**)calloc(100, sizeof(char*));
  sql = "SELECT COUNT(*) FROM test_table;";
  exec_db();
  count = atoi(result[0]);

  sql = (char*)calloc(50, sizeof(char));
  sprintf(sql, "SELECT NAME FROM test_table WHERE ID=%d",10);
  exec_db();
  return 0;

}

Output:

 j_value:0

 argc: 1
 COUNT(*) = 3

 j_value:0

 argc: 1

 name = Jessy

 output[0]:Jessy

 Final output[0]:Jessy

 Final output[1]:(null)

 Final output[2]:(null)

 j_value:1

 argc: 1
 name = Hussain

 output[1]:Hussain

 Final output[0]:Hussain

 Final output[1]:Hussain

 Final output[2]:(null)

 j_value:2

 argc: 1
 name = Shyam

 output[2]:Shyam

 Final output[0]:Shyam

 Final output[1]:Shyam

 Final output[2]:Shyam
Mohamed Hussain
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  • 6
  • Welcome to Stack Overflow! [Please see this discussion on why not to cast the return value of `malloc()` and family in `C`.](http://stackoverflow.com/q/605845/2173917). – Sourav Ghosh Jun 06 '16 at 12:23
  • Where do the variables `count` and `data` come from? Please provide a complete code example. – Support Ukraine Jun 06 '16 at 12:40
  • You only store a copy to sqlite's internal buffer, you do not copy the string to your own buffer. As the sqlite function reuses the buffer between calls to the callback, you are getting the same buffer every time, and can only access the last value. – Karsten Koop Jun 06 '16 at 12:41
  • hi.. I had edited and gave the full code now. kindly refer it. – Mohamed Hussain Jun 06 '16 at 13:19
  • @KarstenKoop , Is there any other way can we able to store the names and access it outside the callback using our own buffer or any other idea – Mohamed Hussain Jun 06 '16 at 13:21
  • you would have to allocate buffers for the `result[i]` and use `strcpy` to copy the returned values to your buffer – Karsten Koop Jun 06 '16 at 13:24
  • Thanks @KarstenKoop.. I found my mistake. I haven't allocated memory dynamically for every pointer location in array of pointer *store[50]. And also idea of strcpy worked. – Mohamed Hussain Jun 07 '16 at 09:06

0 Answers0