how to query in sql the previous date of max date of an item and if only one date is there for an item return that date as result

Question

how to query in sql the previous date of max date of an item and if only one date is there for an item return that date as result. Attaching sample Image for refference

Answer 1

Your question was a little crude and was lacking own attempts to solve this but here you go

create table d(
  item VARCHAR(1),
  expiry_date DATETIME 
);

INSERT INTO d(item, expiry_date)
VALUES
('A','2018-03-08'),
('A','2018-03-11'),
('A','2018-03-31'),
('A','2019-01-12'),
('A','2019-03-01'),
('A','2019-03-21'),
('A','2020-03-01'),
('B','2021-03-26'),
('C','2019-03-01'),
('C','2019-03-21'),
('C','2020-03-01');

;WITH maxdates AS (
  SELECT
    item,
    MAX(expiry_date) max_expiry_minus_1
  FROM d
  WHERE d.expiry_date != (SELECT MAX(expiry_date) FROM d d2 WHERE d.item = d2.item)
  GROUP BY item
)
SELECT 
  d.item,
  d.expiry_date,
  ISNULL(maxdates.max_expiry_minus_1, expiry_date) expecting_result
FROM d
LEFT OUTER JOIN maxdates
  ON d.item = maxdates.item