The problem with static cases is that you are restricted in the size of the database that can be created. Declaring a 1000 element array implies that the database can't have more than 1000 records in it atleast there is no easy way to alter the number of records it can have short of modifying the array definition in the source code and re-compiling.
the sizeof operator returns the allocated size instead of the used size for any object...so in the above case it will return the "sizeof one empRec structure times 10".

That would work only for static cases and in scenario where the last entry was NULL it implies wasting memory since only 5 out of 10 structs can be used.

Determine the size of one empRec structure and malloc'ate memory for it before adding a new record. This way the database size is not limited by the number of elements in the array.
The code snippet below can be put inside a loop to allocate space for a block of at least empRec size bytes followed by prompting the user for input and storing it in one of the elements of the empRec structure members.

Code:

pointer_to_empRec_object = malloc(sizeof(struct empRec));

while () {    /* while loop to capture user input */
    printf("get emp name ");
    fgets()   /* store emp name input above */
    printf("get emp room ");
    fgets()   /* store emp room */
    printf("get emp start date ");
    fgets()   /* store emp start date */
}   /* end of while loop */