#define FMT "INSERT INTO data (v1, v2, v3, v4) VALUES ('%s', '%s', '%s', '%s')"
#define NSTMTS 3

int i;
char *stmts[NSTMTS];

for (i = 0; i < NSTMTS; i++) {
  size_t s;
  char *p;

  /* ... get data into the array f ... */
  s = snprintf(NULL, 0, FMT, f[0], f[1], f[2], f[3]) + 1;
  assert((p = (char *)malloc(s)) != NULL);

  snprintf(p, s, FMT, f[0], f[1], f[2], f[3]);
}

/* ... do something with the statements ... */

for (i = 0; i < NSTMTS; i++)
  free(stmts[i]);