Callback function in sqlite3_exec (C API)

Question

When using the SELECT operation, if there are no results the callback function do not show results in the screen. I am trying to get a way to know, previously, if there are no results. For example, using the SELECT operation I would like to create a IF that will be true when there are no results in the table. Sorry for the bad English.

The code:

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

static int callback(void *data, int argc, char **argv, char **azColName){
    int i;
    fprintf(stderr, "%s: ", (const char*)data);
    for(i=0; i<argc; i++){
        printf("%s = %s\n", azColName[i], argv[i] ? argv[i] : "NULL");
    }
    printf("\n");
    return 0;
}

int main(int argc, char* argv[])
{
    sqlite3 *db;
    char *zErrMsg = 0;
    int rc;
    char *sql;
    const char* data = "Callback function called";

    rc = sqlite3_open("test.db", &db);
    if( rc ){
        fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db));
        exit(0);
    }else{
        fprintf(stderr, "Opened database successfully\n");
    }

    sprintf (sql, "SELECT * from TABLE WHERE ADMIN LIKE ('%s%') AND PASSWORD LIKE ('%s%');", admin, password);

    rc = sqlite3_exec(db, sql, callback, (void*)data, &zErrMsg);

    if( rc != SQLITE_OK ){
        fprintf(stderr, "SQL error: %s\n", zErrMsg);
        sqlite3_free(zErrMsg);
    }else{
        fprintf(stdout, "Operation done successfully\n");
    }
    sqlite3_close(db);
    return 0;
}

oakad · Accepted Answer · 2014-06-05 08:15:58Z

1

If you want a finer grain control over result fetching, than do not use sqlite3_exec - use a lower level API instead, to the tune:

sqlite3_prepare(...);
do {
    sqlite3_step();
    ....
} while (something);
sqlite3_finalize(...);

That's what sqlite3_exec does anyway. sqlite3_step will allow you to detect that no rows were returned and you can do your processing within the loop directly, without the need for callback.

edited Jun 5, 2014 at 8:15

answered Jun 5, 2014 at 1:40

oakad

7,7851 gold badge25 silver badges35 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Callback function in sqlite3_exec (C API)

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related