Postgres 13

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CREATE TABLE t_date(
  t_date_id  int PRIMARY KEY
, valid_from date NOT NULL
, valid_to   date DEFAULT 'infinity')
;

INSERT INTO t_date VALUES
  (1, '2020-01-01', '2020-09-01')
, (2, '2020-01-10', '2020-01-12')
, (3, '2020-01-15', 'INFINITY')
, (4, '2020-01-16', 'INFINITY')  -- shortest among infinities
, (5, '2020-01-14', 'INFINITY')
;
5 rows affected

-- shortest of all
SELECT *
FROM   t_date
WHERE  valid_from <= '2021-01-01'
AND    valid_to   >  '2019-01-01'
ORDER  BY NULLIF(valid_to, 'infinity') - valid_from
        , valid_from DESC
        , t_date_id                -- optional additional tiebreaker
LIMIT  1;


t_date_id
valid_from
valid_to


2
2020-01-10
2020-01-12


-- shortest among infinities?
SELECT *
FROM   t_date
WHERE  valid_from <= '2021-01-01'
AND    valid_to   >  '2021-01-01'
ORDER  BY NULLIF(valid_to, 'infinity') - valid_from
        , valid_from DESC
        , t_date_id                -- optional additional tiebreaker
LIMIT  1;


t_date_id
valid_from
valid_to


4
2020-01-16
infinity