How to order a column which contains date values ?

[ani_89]

I have a credit card user data in the below mormat.

Card_number	Customer_Number	Date_became_member	Memtype
4.67853E+15	58912152	3/15/1994	P
4.67853E+15	58912152	1/1/2000	A
4.67853E+15	58912153	1/9/2001	P
4.67853E+15	58912153	1/7/2002	A
4.67853E+15	58912153	3/4/1993	A
4.67853E+15	58912157	12/23/1995	P
4.67853E+15	58912160	1/17/2000	P
4.67853E+15	58912161	1/26/2000	P
4.67853E+15	58912161	10/27/1995	A
4.67853E+15	58912162	11/5/2002	P
4.67853E+15	58912162	11/9/1993	A
4.67853E+15	58912162	1/26/2002	A

But in my data the date_became_member is not icorrect order.I want to create a data set like

below.

Card_number	Customer_Number	Date_became_member	Memtype
4678527546403500	58912152	3/15/1994	P
4678527546219220	58912152	1/1/2000	A
4678527546976100	58912153	3/4/1993	P
4678527546503750	58912153	1/9/2001	A
4678527546329640	58912153	1/7/2002	A
4678527546768660	58912157	12/23/1995	P
4678527546294870	58912160	1/17/2000	P
4678527546828960	58912161	10/27/1995	P
4678527546666830	58912161	1/26/2000	A
4678527546698310	58912162	11/9/1993	P
4678527546340550	58912162	1/26/2002	A
4678527546612750	58912162	11/5/2002	A

The main logis is that MEMTYPE =P signifies it is a primary customer and it should have minimum 

date of date became member.MEMTYPE=A signifies the add on card of a customer.

Please help me to get my desired output.

[ballardw]

First question is are your dates SAS date values or character? If proc contents shows them with format mmddyy10 or similar then the dates are okay. If not then you likely need to create a SAS date value that will sort correctly.

If I understand what you are wanting something like this:

proc sort data= have;
   by Customer_number date_became_member;
run;

data want;
   set have;
   by Customer_number date_became_member;
   if first.customer_number then Memtype='P';
   else Memtype='A';
run;