LintCode-Logo 查询相距最近的两棵树苗

SELECT MIN(ABS(a.distance - b.distance)) AS shortest_distance
FROM sapling_distances AS a
INNER JOIN sapling_distances b
ON a.id != b.id;

SELECT MIN(distance_diff) AS shortest_distance FROM (
    SELECT  abs(b.distance - a.distance) AS distance_diff FROM sapling_distances a, sapling_distances b
    WHERE a.id <> b.id
) cc
HAVING shortest_distance is not null;

select min(a.distance - b.distance) shortest_distance
from sapling_distances a
    join sapling_distances b on a.distance > b.distance
having shortest_distance is not null;

select min(s2.distance-s1.distance) shortest_distance from
(select distance,@rownum1:=@rownum1+1 r1 
from sapling_distances,(select @rownum1:=0) ra
order by distance) s1,
(select distance,@rownum2:=@rownum2+1 r2 
from sapling_distances,(select @rownum2:=0) rb
order by distance) s2
where s1.r1 = s2.r2-1 having shortest_distance is not null;