# server TO try it OUT: https://rextester.com/l/sql_server_online_compiler -> SQL server
# desired RESULT IS TO SELECT every SECOND VALUE per DAY: (1,2), (2,2), (3,2)

CREATE TABLE test_ts(
    DAY INT,
    val INT
);

INSERT INTO test_ts (DAY, val)
VALUES
    (1,1),
    (1,2),
    (1,3),
    (1,4),
    (2,1),
    (2,2),
    (2,3),
    (2,4),
    (2,5),
    (3,1),
    (3,2),
    (3,3),
    (3,4),
    (3,5);

SELECT * FROM test_ts

SELECT DAY, val FROM test_ts t
WHERE t.val=2
ORDER BY DAY