start date and end date

Question

i only have three rows of date but i need to have four as my output. How do i tell sql to get the last data for the end date and place it in the last row of the start date?

i tried the lag and lead but it seems it does not work in Teradata database i don't know why.

any suggestion will really help or alternative. Just as ask for any clarification or if you need more data.

Answer 1

One possible option: take the set of records of interest, number each row, then self join each row with the following one. Add an extra record for your closing:

WITH numbered AS (
    SELECT effect_date, row_number() OVER (ORDER BY effect_date) AS rownum
      FROM price
      WHERE prod_id='4'
 )

 SELECT *
   FROM ( SELECT a.effect_date AS start_date
                ,b.effect_date AS end_date
            FROM numbered a
                ,numbered b
            WHERE b.rownum = a.rownum + 1

          UNION

          SELECT MAX(effect_date)
                ,TO_DATE('29991231', 'YYYYMMDD')
            FROM numbered
        ) x
   ORDER BY 1