Sorting array of structure for with two structure variable?

I am having trouble sorting the following array.

How do I sort the temp_var[] array based on temp_var[].trade_date and temp_var[].trans_amount ?

typedef struct      
{
    char    trans_d                  [2],      
            trans_amount            [10], 
            trans_me                 [8],
            account                 [10], 
            trans                  [16],
            trade_date              [12],
            setnt_date              [12];
} what_if;

what_if  temp_var[100];

void swap(what_if *a, what_if *b)
{
    tmp = *a;
    *a = *b;
    *b = tmp;
}


void bubbleSort(what_if a[], int size)
{
    for (i=开发者_高级运维0; i<size-1; i++)
    {
        for (j=size-1; j>i; j--)  
            if (strcmp(a[j].trade_date , a[j-1].trade_date) < 0 )
                swap(&a[j], &a[j-1]);
    }
}

int main()
{
    //after read the structure values
    bubbleSort(temp_var,t_count);
}

You simply check the 2nd sorting criteria if the 1st is equal. Please check wether the trans_amount field can be compared this way. The code could be shorter, my intention was to demonstrate how this works.

int first = strcmp(a[j].trade_date , a[j-1].trade_date);
 if ( first == 0 ) {
     if ( strcmp(a[j].trans_amount , a[j-1].trans_amount) < 0 )
         swap(&a[j], &a[j-1]);
 }
 else if ( first < 0 ) {
    swap(&a[j], &a[j-1]);
 }