Assign certain data to a struct with sqlite3 - c

Question

I've got this structure in C:
typedef struct{
char *NOMBRE;
char *APELLIDO;
int DNI;
char *FECHA_NACIMIENTO;
int TELEFONO;
char *EMAIL;
char *DOMICILIO;
long N_SS ;
long N_CUENTA ;
char *PASSWORD;
} Usuario;
Now that I've got the structure, I'd like to, through a SQL statement, assign certain data from table to a structure.
This is my method:
void bd_sacarDatosUsuario(char *user) {
sqlite3 *db;
char *zErrMsg = 0;
const char* data = "Callback function called";
char sql[70];
char sql2[10];
char user2[10];
strcpy(sql, "SELECT * FROM DATOS_PERSONALES WHERE DNI='");
int rc = sqlite3_open("BD/gimud.db", &db);
if (rc) {
fprintf(stdout, "Can't open database: %s\n", sqlite3_errmsg(db));
} else {
fprintf(stdout, "Opened database successfully\n");
}
strcpy(sql2, "';");
strcpy(user2, user);
strcat(sql, user2);
strcat(sql, sql2);
printf("%s\n", sql);
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, "Consulta creada con exito\n");
}
sqlite3_close(db);
}
How could I, in a callback function, assign the data to Usuario u? I mean:
Usuario u;
u.NOMBRE = argv[0]; // and so on...

Answer 1

First of all, I would like to mention that the code below might not be the final code you were looking for but it could help you to understand how a callback function works.
If the callback function of the 3rd argument to sqlite3_exec() is not NULL, then it is invoked for each result row coming out of the evaluated SQL statements. You can pass an additional argument to the callback function, this is where you will have a chance to save data from the table to your so-called Usuario structure. The fourth argument of the callback serves for this purpose.
For demonstration purpose the code below does the following:
Opens the database
Creates a table with three columns, including ID, NAME and PASSWORD fields
Inserts a row into the table(ID=1, NAME=PETER, PASSWORD=ORANGE)
Allocates space for the structure
Executes the select statement and INVOKES THE CALLBACK() function which stores the data.
#include <stdio.h>
#include <stdlib.h>
#include <sqlite3.h>
#include <string.h>
typedef struct Usuario{
char *name;
char *password;
} Usuario;
int callback(void *Usuario, int argc, char **argv, char **azColName) {
struct Usuario *tmp = (struct Usuario *)Usuario;
char missing[] = "MISSING";
tmp->name = (char *)malloc(sizeof(char) * strlen(argv[1]));
tmp->name = argv[1] ? argv[1] : (char*)"NULL";
tmp->password = (char *)malloc(sizeof(char) * strlen(argv[2]));
tmp->password = argv[2] ? argv[2] : (char*)"NULL";
return 0;
}
void bd_sacarDatosUsuario() {
sqlite3 *db;
char *zErrMsg = 0;
int rc;
// Open database
rc = sqlite3_open("test.db", &db);
if( rc ) {
fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db));
return ;
} else {
fprintf(stderr, "Opened database successfully\n");
}
/* Create table statement */
const char *sql = "CREATE TABLE TEST(" \
"ID INT PRIMARY KEY NOT NULL," \
"NAME CHAR(50) NOT NULL," \
"PASSWORD CHAR(50) NOT NULL);";
rc = sqlite3_exec(db, sql, NULL, 0, &zErrMsg);
if( rc != SQLITE_OK ){
fprintf(stderr, "SQL error: %s\n", zErrMsg);
sqlite3_free(zErrMsg);
} else {
fprintf(stdout, "Success\n");
}
// Insert test data
sql = "INSERT INTO TEST(ID, NAME, PASSWORD) VALUES(1, \"PETER\", \"ORANGE\");";
rc = sqlite3_exec(db, sql, NULL, 0, &zErrMsg);
if( rc != SQLITE_OK ){
fprintf(stderr, "SQL error: %s\n", zErrMsg);
sqlite3_free(zErrMsg);
} else {
fprintf(stdout, "Success\n");
}
// Allocate space for the structure
struct Usuario *u = (struct Usuario *)malloc(sizeof(struct Usuario));
sql = "SELECT * FROM TEST";
rc = sqlite3_exec(db, sql, callback, u, &zErrMsg);
if( rc != SQLITE_OK ){
fprintf(stderr, "SQL error: %s\n", zErrMsg);
sqlite3_free(zErrMsg);
} else {
fprintf(stdout, "Success\n");
}
sqlite3_close(db);
printf("Hi my name is: %s with password of %s\n", u->name, u->password);
}
int main() {
bd_sacarDatosUsuario();
}
Change the structure according to your needs. Note that you should check if malloc returns a non-NULL value and of course deallocate it after you do not need that.