SQL Server 2017

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3 rows affected

DECLARE @Id          INT = 1102670655; -- item being moved
DECLARE @newPosition INT = 0;          -- and its new position

DECLARE @Plan_Id INT;
DECLARE @oldPosition INT;

SELECT
    @Plan_Id = Plan_Id,
    @oldPosition = sequence_no
FROM planRecords
WHERE Id = @Id;

UPDATE planRecords SET sequence_no = CASE
    WHEN Id = @Id THEN @newPosition                       -- item being moved gets new position without question
    WHEN @oldPosition < @newPosition THEN sequence_no - 1 -- item moved up, other items must be pushed down
    WHEN @oldPosition > @newPosition THEN sequence_no + 1 -- item moved down, other items must be pushed up
END
WHERE Plan_Id = @Plan_Id AND sequence_no BETWEEN          -- only update items with same Plan_Id and position between old and new pos
    CASE WHEN @oldPosition < @newPosition THEN @oldPosition ELSE @newPosition END AND
    CASE WHEN @oldPosition > @newPosition THEN @oldPosition ELSE @newPosition END;

SELECT *
FROM planRecords
ORDER BY Plan_Id, sequence_no

Id	Plan_Id	sequence_no
1102670655	1167096719	0
1132507748	1167096719	1
1166210290	1167096719	2