How to get start date and end date in sql?

Question

I have a small table that looks like this:

PLAN    YRMTH
A2BKG   197001
A2BKG   200205
A2BKG   200308
A2BKG   200806

From this table, how do I get a table such as the one below?

   PLAN STARTDATE   ENDDATE
    A2BKG   197001      200205
    A2BKG   200205      200308
    A2BKG   200308      200806
    A2BKG   200806      NULL 

Answer 1

Try this

;with cte as 
(select *, ROW_NUMBER() over (partition by [plan] order by yrmth) rn from yourtable)
    select 
        t1.[plan],
        t1.YRMTH as startdate,
        t2.YRMTH as enddate
    from cte t1
        left join cte t2 on t1.[plan]=t2.[plan]
            and t1.rn=t2.rn-1