How to sort a group of structures in C - c

Question

I made a 4 variables structures and assigned values just to age.
struct database {
int id_number;
int age;
float salary;
};
main()
{
struct database employee[4];
struct database current; // Used later in my attempted sorting
employee[1].age = 12;
employee[2].age = 112;
employee[3].age = 2;
employee[4].age = 22;
I tried various ways to attempt to sort these but all failed,
for example:
for(i = 0; i < 4; i++)
{
current = employee[i];//"current" was previously assigned to the same type of struct
j = i;
while(employee[j-1].age > current.age)
{
employee[j] = employee[j-1];
j = j-1;
}
employee[j] = current;
}

Answer 1

Many errors, as pointed by others in comments.
(Out of bound array access, sorting algorithm is not correct, etc. )
For sorting array of struct, simplest way would be to use qsort
where you need to define a custom comparator, something like following :
typedef struct database db;
int sort_by_age(void *a, void *b)
{
db *_a = (db *)a;
db *_b = (db *)b;
if( _a->age > _b->age ) return -1;
if( _a->age == _b->age ) return 0;
return 1;
}
And then use it like,
int no_of_employee = 4;
qsort( employee, no_of_employee, sizeof(db), sort_by_age );