how to get next/prev row from mysql by group - mysql

Question

I have a table on MySQL like this:
ID Name Group
1 One A
2 Two B
3 Three A
4 Fore C
5 Five B
6 Six A
7 Seven B
I want to get the previous row/ next row in same group from my selected row. Like if I have selected row with ID=5, now how can I get the same group previous row(ID=2) when I haven't any information about the row and same with next row(ID=7).

Answer 1

You are looking for LEAD or LAG with Windows function, but it's was supported mysql higher version than 8.0. so you can instead write a subquery on select
look like this.
TestDLL
CREATE TABLE T(
ID int,
Name VARCHAR(100),
`Group` VARCHAR(5)
);
INSERT INTO T VALUES (1,'One','A');
INSERT INTO T VALUES (2,'Two','B');
INSERT INTO T VALUES (3,'Three','A');
INSERT INTO T VALUES (4,'Fore','C');
INSERT INTO T VALUES (5,'Five','B');
INSERT INTO T VALUES (6,'Six','A');
INSERT INTO T VALUES (7,'Seven','B');
Query
select *,IFNULL((
SELECT t2.ID
FROM T t2
WHERE t1.Group = t2.Group and t1.ID > t2.ID
ORDER BY t2.ID DESC
LIMIT 1
),t1.ID)previousID
,IFNULL((
SELECT t2.ID
FROM T t2
WHERE t1.Group = t2.Group and t1.ID < t2.ID
ORDER BY t2.ID
LIMIT 1
),t1.ID) nextID
from T t1
[Results]:
| ID | Name | Group | previousID | nextID |
|----|-------|-------|------------|--------|
| 1 | One | A | 1 | 3 |
| 2 | Two | B | 2 | 5 |
| 3 | Three | A | 1 | 6 |
| 4 | Fore | C | 4 | 4 |
| 5 | Five | B | 2 | 7 |
| 6 | Six | A | 3 | 6 |
| 7 | Seven | B | 5 | 7 |
If your mysql support windows function, you can try this.
select *,
LAG(ID)previousID,
LEAD(ID) nextID
from T
sqlfiddle