I have a simple table called users with the following data:
id | hops
1 | 3
2 | 1
3 | 5
4 | 2
5 | 6
6 | 5
I want to make a prev/next navigation according to hops sorted descending. I use the following to query to sort descending:
SELECT * FROM users ORDER BY hops DESC, id DESC
This is the result:
id | hops
5 | 6
6 | 5
3 | 5
1 | 3
4 | 2
2 | 1
Now what I want is that when I input any id in a mysql query I get the previous and next ids according to sorting above. For example:
For id 5 (In this case id=5 has the highest hops so no previous records before it):
id (current) | hops (current) | id (prev) | hops (prev) | id (next) | hops (next)
5 | 6 | NULL | NULL | 6 | 5
For id 6:
id (current) | hops (current) | id (prev) | hops (prev) | id (next) | hops (next)
6 | 5 | 5 | 6 | 3 | 5
For id 3:
id (current) | hops (current) | id (prev) | hops (prev) | id (next) | hops (next)
3 | 5 | 6 | 5 | 1 | 3
For id 1:
id (current) | hops (current) | id (prev) | hops (prev) | id (next) | hops (next)
1 | 3 | 3 | 5 | 4 | 2
For id 4:
id (current) | hops (current) | id (prev) | hops (prev) | id (next) | hops (next)
4 | 2 | 1 | 3 | 2 | 1
For id 2 (In this case id=2 has the lowest hops so no next records after it)
id (current) | hops (current) | id (prev) | hops (prev) | id (next) | hops (next)
2 | 1 | 4 | 2 | NULL | NULL
Thanks
Try:
select cp.*, n.id id_next, n.hops hops_next
from
(select c.id id_current, c.hops hops_current, p.id id_previous, p.hops hops_previous
from
(select * from users where id = ?) c
left join users p on c.hops < p.hops or (c.id < p.id and c.hops = p.hops)
order by p.hops, p.id limit 1) cp
left join users n
on cp.hops_current > n.hops or (cp.id_current > n.id and cp.hops_current = n.hops)
order by n.hops desc, n.id desc limit 1
(SQLFiddle here )
This is the weirdest users table I've seen so far. Anyway here's one way (although I have to admit it's a little complicated)...
DROP TABLE IF EXISTS test;
CREATE TABLE test(id INT NOT NULL AUTO_INCREMENT PRIMARY KEY,hops INT NOT NULL);
INSERT INTO test VALUES
(1 ,3),(2 ,1),(3,5),(4 ,2),(5 ,6),(6 ,5);
SELECT c.id id_curr
, c.hops hops_curr
, p.id id_prev
, p.hops hops_prev
, n.id id_next
, n.hops hops_next
FROM
(
SELECT a.*
, COUNT(*) new_rank
FROM
( SELECT x.*
, COUNT(*) rank
FROM test x
JOIN test y
ON y.hops >= x.hops
GROUP
BY x.id
) a
JOIN
( SELECT x.*
, COUNT(*) rank
FROM test x
JOIN test y
ON y.hops >= x.hops
GROUP
BY x.id
) b
ON b.rank < a.rank
OR (b.rank = a.rank AND b.id >= a.id)
GROUP
BY a.id
)c
LEFT
JOIN
(
SELECT a.*
, COUNT(*) new_rank
FROM
( SELECT x.*
, COUNT(*) rank
FROM test x
JOIN test y
ON y.hops >= x.hops
GROUP
BY x.id
) a
JOIN
( SELECT x.*
, COUNT(*) rank
FROM test x
JOIN test y
ON y.hops >= x.hops
GROUP
BY x.id
) b
ON b.rank < a.rank
OR (b.rank = a.rank AND b.id >= a.id)
GROUP
BY a.id
) p
ON p.new_rank = c.new_rank-1
LEFT
JOIN
(
SELECT a.*
, COUNT(*) new_rank
FROM
( SELECT x.*
, COUNT(*) rank
FROM test x
JOIN test y
ON y.hops >= x.hops
GROUP
BY x.id
) a
JOIN
( SELECT x.*
, COUNT(*) rank
FROM test x
JOIN test y
ON y.hops >= x.hops
GROUP
BY x.id
) b
ON b.rank < a.rank
OR (b.rank = a.rank AND b.id >= a.id)
GROUP
BY a.id
) n
ON n.new_rank = c.new_rank+1
ORDER
BY c.hops DESC
, c.id DESC;
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