为循环中的项目分配编号-SAS

Question

Each ID number has several items associated with it. For every item under each ID, I want to assign a number to it. I would like the number to start at 1 for each ID. How would I do this in SAS? I'm guessing I can use a type of loop statement. Below is an example of my goal. Thanks for your help.

EDIT: I have to add another layer to this problem. If the ID has item = SPECIAL, I want that record to always be assigned 1 and have the other items follow it.

+----+----------+----------+
|ID  |Item      |Assignment|
+----+----------+----------+
|A001|SPECIAL   |1         |
+----+----------+----------+
|A001|Orange    |2         |
+----+----------+----------+  
|A001|Pineapple |3         |
+----+----------+----------+
|A002|Banana    |1         |
+----+----------+----------+
|A002|Strawberry|2         |
+----+----------+----------+
|A002|Pear      |3         |
+----+----------+----------+
|A002|Watermelon|4         |
+----+----------+----------+
|A003|SPECIAL   |1         |
+----+----------+----------+
|A003|Banana    |2         |
+----+----------+----------+
|A003|Apple     |3         |
+----+----------+----------+

Answer 1

The easiest way to do it - with BY statement and automatic variables FIRST and LAST. Original dataset should be sorted by ID before.

data have;
    input ID $ Item $;

    datalines;
A001 SPECIAL
A001 Orange
A001 Pineapple
A002 Banana
A002 Strawberry
A002 Pear
A002 Watermelon 
A003 SPECIAL   
A003 Banana
A003 Apple
;
run;

data want;
    set have;
    by ID;
    if FIRST.ID then Assignment=1;
    else Assignment+1;
run;

Regarding your additional layer: just add one more condition to the IF-statement:

 `if FIRST.ID or item='SPECIAL' then Assignment=1;`