Sorting a 2D array with qsort

I'm trying to sort 2d array. First i sort it by column, then by rows. Column by column is working but row by row not. What's wrong in this code?

int scmpr (const void *a, const void *b){ 
return strcmp((const char*)a, (const char*)b);
}

int main(void){
  int i,j;

  char **tab;
  tab=(char**)malloc(sizeof(char*)* 10); 

  for(i=0; i<10; i++){
    tab[i]=(char*)malloc(sizeof(char)*15);
  }

  for(i=0; i<10; i++){
    for(j=0; j<15; j++){
      tab[i][j]=rand()%20+'b';
      printf("%c ", tab[i][j]);
    }
    puts("");
  }
  for (i = 0; i<10; i++){
    qsort(&tab[i][0], 15, sizeof(char), scmpr); 
  }
  qsort(tab, 10, sizeof(char), scmpr); //<-- doesn't work

    for(i=0; i<10; i++){
      for(j=0; j<15; j++){
        printf("%c ", tab[i][j]);
      }
    puts("");
    } 
  puts("");
  return 0;
  }