Assigning serial number and date to new observation

[ameshram28]

I maintain a dataset named as "XYZ" . eg. XYZ contains only one column as show name A, B, C, X, Y, Z....

Dataset XYZ:

Show_name

A

B

C

X

Y

Z

Every week I update the dataset XYZ and sort them to get dataset ABC with the below code.     

/*Sort all show name in ascending order*/

Proc Sort Data=XYZ;

By Show_Name;

Run;

/*Create Serial number and Date stamp*/

Data ABC;

Set XYZ;Format Date mmddyy.;

Serial_no=_n_;

Date=today();

Run;

Dataset ABC:

Serial No	Date	Show_Name
1	3/23/2016	A
2	3/23/2016	B
3	3/23/2016	C
4	3/23/2016	X
5	3/23/2016	Y
6	3/23/2016	Z

 Now, in future when I refresh XYZ and see a new show in the list (eg. P and Q).so instead of sorting and giving serial number. I just want to sort new show_name and give serial number to P and Q. only. 

Desired Output:

Serial No	Date	Show_name
1	3/23/2016	A
2	3/23/2016	B
3	3/23/2016	C
4	3/23/2016	X
5	3/23/2016	Y
6	3/23/2016	Z
7	3/24/2016	P
8	3/24/2016	Q

[ballardw]

Please describe how you would add the values of P and Q on the later date.

Different approaches  would be open depending on your method.

[ameshram28]

I maintain a dataset named XYZ, which I refresh on monthly basis. 

[PGStats]

Varaible?

Data ABC;
Set XYZ end=done;
output;
if done then do;
	date = today();
	serial_no = serial_no + 1;
	varaible = "P";
	output;
	serial_no = serial_no + 1;
	varaible = "Q";
	output;
	end;
Run;